HP StorageWorks 12000 Guide

HP VLS Solutions Guide
Design Guidelines for Virtual Library Systems with
Deduplication and Replication
Abstract
This document describes the HP Virtual Library System and its concepts including automigration, deduplication, and replication,
to help you define and implement your virtual tape library system. It includes best practices for working with specific backup
applications. This document is intended for use by system administrators who are experienced with setting up and managing
system backups over a SAN.
**AG306-96032**
HP Part Number: AG306-96032
Published: June 2011
Edition: Ninth

© Copyright 2005, 2011 Hewlett-Packard Development Company, L.P.
The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express
warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall
not be liable for technical or editorial errors or omissions contained herein.
Acknowledgements
Microsoft, Windows, Windows XP, and Windows NT are U.S. registered trademarks of Microsoft Corporation.
Oracle is a registered US trademark of Oracle Corporation, Redwood City, California.
Revision History
Revision History
June 2011Revision AG306-96032
release of firmware version 6.0.0.2 and removal of D2D information
September 2010Revision AG306-96031
release of firmware version 3.4.0
March 2010Revision AG306-96028
release of firmware version 3.3.1
September 2009Revision AG306-96026
release of firmware version 3.2.1

Contents
1 Introduction...............................................................................................8
2 Concepts...................................................................................................9
Disk-based Backup and Virtual Tape Libraries...............................................................................9
Problems Addressed by Virtual Tape Libraries..........................................................................9
Integration of Disk in Data Protection Processes........................................................................9
Where Virtual Tape Fits in the Big Picture................................................................................9
HP VLS and D2D Portfolio...................................................................................................10
Typical VLS Environments....................................................................................................11
Typical D2D Environments...................................................................................................11
What are the Alternatives?..................................................................................................12
Physical Tape................................................................................................................12
NAS............................................................................................................................12
Application-based Disk Backup.......................................................................................12
Business Copy..............................................................................................................13
Deduplication........................................................................................................................14
Introduction.......................................................................................................................14
HP Deduplication Solutions.................................................................................................14
Deduplication Ratios..........................................................................................................15
Target-based Deduplication.................................................................................................16
Tape Oversubscription........................................................................................................16
Replication............................................................................................................................17
Introduction to Replication...................................................................................................17
HP Replication Solutions.....................................................................................................17
Replication Deployment Options..........................................................................................20
Backup Application Interaction with Replication.....................................................................22
Replication Limitations........................................................................................................23
3 Backup Solution Design Considerations.......................................................24
Analyze the Existing Environment..............................................................................................24
Consider How you Want to Back Up your Data to the VLS......................................................24
Consider How you Want to Copy the Backup Data to an Off-site Location.................................26
Consider Speed and Ease of the Restore as well as the Backup................................................26
Single Library vs. Multiple Libraries...........................................................................................26
Single Library....................................................................................................................26
Benefits of Single Library Systems....................................................................................27
Considerations for Single Library Systems.........................................................................27
Multiple Library.................................................................................................................28
Benefits of Multiple Library Systems..................................................................................28
Multiplexing, Multistreaming, and Multipathing..........................................................................29
Multiplexing......................................................................................................................29
Multistreaming...................................................................................................................29
Multipathing.....................................................................................................................29
Blocksize and Transfer Size......................................................................................................30
LAN-free Backups...................................................................................................................30
Retention Planning..................................................................................................................30
Future Data Growth.................................................................................................................31
Considerations for Copies........................................................................................................31
Copy to Physical Tape through the Backup Application...........................................................31
Media Server Considerations..........................................................................................32
Benefits of Copying to Physical Tape through the Backup Application...................................33
Considerations for Copying to Physical Tape through the Backup Application........................33
Contents 3

Copy to Tape using VLS Automigration.................................................................................33
Benefits of Echo Copy....................................................................................................34
Considerations of Echo Copy..........................................................................................34
Copy to Remote Disk Backup Device using Replication............................................................35
Benefits of Replication....................................................................................................35
Considerations of Replication..........................................................................................35
Creating Archive Tapes from the Replication Target................................................................35
Considerations for Restores......................................................................................................36
Restoring from Disk Backup Device.......................................................................................36
Restoring from Backup Application-created Tape Copy............................................................36
Restoring from the Replication Target....................................................................................36
Performance Bottleneck Identification.........................................................................................37
Backup SAN Design Guidelines...............................................................................................37
General SAN Design Considerations....................................................................................37
SAN Zoning......................................................................................................................37
Operating System Tape Configuration..................................................................................38
LUN Masking and Mapping................................................................................................40
4 VLS Devices.............................................................................................42
VLS Defined...........................................................................................................................42
Prime Environments............................................................................................................43
VLS Benefits......................................................................................................................43
VLS9000–series and VLS9200 Configurations.......................................................................44
VLS Technical Specifications................................................................................................45
How it Works.........................................................................................................................52
VLS Scalability..................................................................................................................52
VLS Automatic Performance Load Balancing..........................................................................54
VLS Warm Failover............................................................................................................55
Implementation.......................................................................................................................55
Capacity Licensing.............................................................................................................55
Virtual Libraries/drives/cartridge Configuration.....................................................................56
EVA Preparation................................................................................................................57
Storage Pooling.................................................................................................................59
VLS9000 Storage Pooling..............................................................................................60
VLS Gateway Storage Pooling.........................................................................................61
VLS Sizing.............................................................................................................................61
Outlining the Steps.............................................................................................................61
Considerations..................................................................................................................62
EVA Performance Sizing (VLS12X00 Gateway)......................................................................62
Sizing/implementation Examples.........................................................................................63
Example 1 VLS Sizing for Performance and Capacity.........................................................63
Example 2 Testing Backup to Tape vs. Backup to VLS.........................................................63
Example 3: VLS12000 EVA Sizing Without Deduplication..................................................64
Example 4: VLS12000 EVA Sizing With Deduplication......................................................64
VLS Blueprints........................................................................................................................64
Reduce Backup Window (No Deduplication).........................................................................65
Large Scale Backup Consolidation (No Deduplication)............................................................66
Managing Data Retention and Reducing Backup Storage Costs...............................................67
Full Enterprise Backup and Disaster Recovery Capability.........................................................68
Multi-data Center Replication to a Common Disaster Recovery Site...........................................69
VMWare Backup Environment with ESXi................................................................................71
VMWare Backup Environment with ESX4 and VCB-based Backups...........................................72
Larger VMWare Environment with ESX4 and HP Data Protector ZDB IR Integration with VMWare
Consolidated Backup.........................................................................................................74
Large Enterprise Cross-site Backup with Deduplication and Inbuilt Disaster Recovery...................76
4 Contents

Combining D2D and VLS in an End-to-end Solution for ROBO/Regional DCs and Main Data
Center using HP Data Protector............................................................................................77
5 Automigration..........................................................................................79
Echo Copy Concepts...............................................................................................................79
Implementation.......................................................................................................................79
Echo Copy Pools................................................................................................................79
Automigration Policy...........................................................................................................80
Automigration Setup...........................................................................................................81
Design Considerations............................................................................................................83
Automigration Use Models..................................................................................................83
Backup to Non-shared Virtual Libraries.............................................................................83
Backup to a Shared Virtual Library..................................................................................84
Sizing the Tape Library.......................................................................................................85
Restoring from Automigration Media.........................................................................................85
6 Accelerated Deduplication.........................................................................87
How it Works.........................................................................................................................87
Accelerated Deduplication Implementation.................................................................................91
Supported Backup Applications and Data Types....................................................................92
Licensing..........................................................................................................................92
Migrating your Existing Backup Data....................................................................................92
Configuration and Reporting...............................................................................................93
Handling the Device Out of Capacity Condition....................................................................93
Design Considerations............................................................................................................94
Performance......................................................................................................................94
Capacity Sizing.................................................................................................................95
Optimum Record Sizing......................................................................................................95
Optimizing File Server Deduplication....................................................................................95
Media Management..........................................................................................................95
Client and Backup Job Naming...........................................................................................96
Disabling Deduplication on Specific Backup Policies...............................................................97
Separate Database Full Backups from Incremental Backups......................................................97
7 Replication..............................................................................................98
How it Works.........................................................................................................................98
Replication of Incremental Backups.......................................................................................99
Multi-node Replication Scaling...........................................................................................100
VLS Replication Implementation..............................................................................................100
Licensing........................................................................................................................100
Replication Setup.............................................................................................................101
Implementing the Initialization Process................................................................................105
Physical Tape Initialization............................................................................................106
WAN Initialization......................................................................................................107
Co-location Initialization...............................................................................................108
Continuing Role for Physical Tape..................................................................................109
Reporting........................................................................................................................109
Status of LAN/WAN Replication Connection..................................................................110
Source Device Replication Status...................................................................................110
Target Device Replication Status....................................................................................112
Replication Job Status..................................................................................................112
Replication Job History.................................................................................................112
Design Considerations..........................................................................................................113
Advanced Replication Job Control......................................................................................113
Link Sizing......................................................................................................................115
Basic Calculations.......................................................................................................116
Contents 5

Device Sizing..................................................................................................................120
VLS Replication Data Recovery Options...................................................................................120
Restore Directly from the VLS Target Device..........................................................................120
Restore the VLS over the LAN/WAN..................................................................................122
Rebuilding Source Device and Re-establishing Replication.....................................................123
Rebuilding Target Device and Re-establishing Replication......................................................123
Creating Archive Tapes from the Target...............................................................................124
ISV Import Email Format...............................................................................................125
Email Processing Example Script...................................................................................125
8 Non-deduplicated Replication..................................................................127
Replicating a Subset of Virtual Cartridges - a Use Case.............................................................128
9 VLS Configuration and Backup Application Guidelines................................129
SAN Configuration Guidelines...............................................................................................129
Device Configuration Preparation............................................................................................129
Basic VLS Device Configuration.........................................................................................130
Basic Backup Application Configuration..............................................................................131
Deduplication Preparation.................................................................................................132
Replication Preparation.....................................................................................................133
HP Data Protector.................................................................................................................135
HP Data Protector Application Overview.............................................................................135
Data Protector General Guidelines.....................................................................................136
Data Protector Deduplication Guidelines.............................................................................137
Data Protector Import Example Script..................................................................................138
Symantec NetBackup............................................................................................................139
Symantec NetBackup Application Overview........................................................................139
NetBackup General Guidelines.........................................................................................140
NetBackup Deduplication Guidelines.................................................................................140
NetBackup Import Example Script......................................................................................141
IBM TSM.............................................................................................................................141
IBM TSM Application Overview.........................................................................................141
TSM General Guidelines...................................................................................................143
TSM Deduplication Guidelines...........................................................................................144
All Firmware Versions..................................................................................................144
Firmware Version 3.4...................................................................................................146
Firmware Version 6.0...................................................................................................147
TSM Useful Queries..........................................................................................................147
EMC NetWorker..................................................................................................................148
EMC NetWorker Application Overview..............................................................................148
Networker General Guidelines..........................................................................................149
Networker Deduplication Guidelines..................................................................................150
Oracle RMAN Scripting........................................................................................................151
Generic RMAN Configuration Optimization........................................................................151
Fully-optimized RMAN Configuration for Data Protector.........................................................152
Fully-optimized RMAN Configuration for NetBackup and Networker.......................................152
Fully-optimized RMAN Configuration for TSM......................................................................153
10 Support and Other Resources.................................................................154
Related Information...............................................................................................................154
Documents......................................................................................................................154
Websites........................................................................................................................154
Contacting HP......................................................................................................................154
Before you contact HP......................................................................................................154
HP contact information.....................................................................................................155
Subscription Service..............................................................................................................155
6 Contents

Document Conventions and Symbols.......................................................................................155
Glossary..................................................................................................157
Index.......................................................................................................158
Contents 7

1 Introduction
Welcome to virtual tape libraries. This guide describes the HP Virtual Library System and its concepts
including automigration, deduplication, and replication, to help you define and implement your
virtual tape library system. It includes best practices for working with specific backup applications.
Although every user environment and every user’s goals are different, there are basic considerations
that can help you use the VLS effectively in your environment. The VLS is a powerful and flexible
family of devices. Because it can be productively used in so many ways, there is no “best”
configuration. But by asking yourself the questions and following the parameters outlined in this
guide, you can define and implement a system that is best for your particular environment and
applications.
Before proceeding, make sure you are familiar with the items below.
•Tape backup technologies, tape libraries, and backup software.
•SAN environments.
•Fibre Channel technology.
See the “Glossary” for the definition of acronyms and specific terms.
NOTE: This guide replaces the HP StorageWorks Virtual Library System Solutions Guide, the HP
StorageWorks Deduplication and replication solutions guide, and the HP StorageWorks
Deduplication solutions guide.
8 Introduction

2 Concepts
Disk-based Backup and Virtual Tape Libraries
Problems Addressed by Virtual Tape Libraries
You can optimize your backup environment with VLS and D2D if you are:
•Not meeting backup windows due to slow servers.
•Not consistently streaming your tape drives.
•Dealing with restore problems caused by interleaving.
•Performing many restores (such as single file or small database restores).
•Backing up data that has a short life.
•Having issues with backup reliability.
•Using snapshot and clone technology for non-critical data (which makes the storage
inappropriately expensive for the nature of the data).
•Looking to deemphasize tape in your environment. Bear in mind that removable media remains
valuable in its own right and for particular purposes such as site protection and protection
from malicious attack (for example, viruses and hackers), data distribution, data copy, archive,
and regulatory compliance.
•Improving media management. You can keep incremental backups on virtual tape and send
full backups straight to tape.
Integration of Disk in Data Protection Processes
Globalization, 24x7 environments, and consolidation are driving more rigorous data protection
requirements. To address these requirements, disk is frequently introduced into the backup process.
In disk solutions, data is backed up from an application server (disk) over a dedicated SAN to a
disk-based system and from there to a traditional tape library. This provides enhanced solutions
for slow servers, single-file restores, and perishable data.
One of the particular benefits of the VLS and D2D is that they make a disk array look to your
backup server like a tape library. Implementation requires no new software and no significant
redesign of your backup processes. On the VLS300 and VLS12000 Gateways, because they are
attached to an EVA, the existing Fibre Channel infrastructure and management framework is used
and there is no new management server required.
NOTE: Tape holds its value for ease of vaulting, economical long-term retention, and immutability
(with WORM). It is the last step in your data’s storage cycle.
Where Virtual Tape Fits in the Big Picture
Virtual libraries are not necessarily the only piece of your backup plans, but they can be an integral
piece of a successful solution. Figure 1 (page 10) illustrates the common backup technologies and
their relative benefits and costs.
Disk-based Backup and Virtual Tape Libraries 9

Figure 1 Common Backup Technologies
See What are the Alternatives? for more discussion of the other potential players in your backup
environment.
HP VLS and D2D Portfolio
HP offers a wide range of disk-based backup products to help organizations meet their data
protection challenges. Moving the front line of data protection from tape to disk reduces
administrative overhead; daily backups are entirely automated and involve no tape handling to
provide better backup reliability and less worry.
The entry level D2D100 series Backup System meets the needs of small businesses as a low-cost
solution that does not incorporate deduplication technology. The D2D2500 is well suited for remote
and branch offices and small IT environments, while the more powerful D2D4000 and D2D4100
are designed for medium-sized companies and small data centers. The D2D2500, D2D4000 and
D2D4100 products include HP Dynamic deduplication, which provides low cost and flexibility to
meet the needs of smaller IT environments.
HP Virtual Library Systems are known for their easy integration, simple management, performance
and capacity scalability, and fast restores. The VLS6000, VLS9000 and VLS12000 EVA Gateway
are designed for medium to large-scale enterprises. They feature Accelerated deduplication,
available by license, to deliver the best backup performance and scalability for high availability
data center environments.
10 Concepts

Figure 2 HP Virtual Tape Library Product Range
Typical VLS Environments
In a typical enterprise backup environment, there are multiple application servers backing up data
to a shared tape library on the SAN. Each application server contains a remote backup agent that
sends the data from the application server over the SAN fabric to a tape drive in the tape library.
However, because backup over the SAN is single-threaded (a single host is backing up to a single
tape drive), the speed of any single backup can be limited. This is particularly true when the
environment has high-speed tape drives such as Ultrium 2 or Ultrium 3. The hosts simply cannot
keep the drives streaming at capacity.
NOTE: HP Ultrium drives will adjust the tape speed to match the data stream to prevent
“back-hitching.” However, the tape drive is still not operating at optimal performance and cannot
share bandwidth with another backup job.
Enterprise data centers with slow SAN hosts in the environment may be unable to utilize the full
performance of high-speed tape drives. Also, shared tape libraries on the SAN can be difficult to
configure both in the hardware and in the data protection software.
Typical D2D Environments
In a typical entry-level or mid-range backup environment, the backup application is performing
LAN backups to a dedicated (non-shared) backup target such as a tape library connected to the
single backup server. Multiple instances of the backup application will generally each require their
own dedicated backup target. These environments may also be remote branch offices, each with
their own local backup application.
As with the VLS, the backup speed of a single host backing up to a single tape drive is normally
limited by the host (which cannot stream high-speed tape drives such as LTO), so currently tape
backups use multiplexing to interleave multiple hosts’ backups together into a single tape drive
impacting restore performance. The addition of a D2D device to these environments allows
de-multiplexing of the backups so that restore performance is improved, the deduplication allows
Disk-based Backup and Virtual Tape Libraries 11

for a longer retention time on disk without needing significantly higher disk capacities, and the
deduplication-enabled replication allows cost-effective off-site copying of the backups for disaster
protection.
What are the Alternatives?
Alternatives to virtual tape solutions include:
•Physical Tape
•NAS (network attached storage)
•Application-based Disk Backup (disk to disk, backup to disk, disk to disk to tape)
•Business Copy (snapshot and clone solutions)
Physical Tape
Tape is the foundation for data protection and should be a part of most data protection solutions
(except those with highly perishable data). Consider a direct-to-tape scheme if:
•You are doing large image backups (such as databases), or
•Your servers can stream the tape drives.
and
•You do not need fast single file restore, or
•Your current backup window is not strained.
NAS
An alternative to a virtual library is a NAS device acting as a backup target (via NFS or CIFS
network file system protocols). However, this protocol has significant performance and scaling
limitations; writing backups over TCP/IP and NFS/CIFS to the NAS target uses much more CPU
on the backup infrastructure compared to Fibre Channel SAN. In addition, a NAS mount point
does not scale to the size of an enterprise virtual tape library. For example, a VLS can present a
single virtual library target containing multiple petabytes of tape capacity with all backup jobs
configured to use the one common shared high-performance high-capacity VLS backup device.
Consider a NAS target if you:
•Do not have high performance requirements.
•Do not want to run SAN backups.
•Do not need the backup target to significantly scale capacity or performance.
•Want to run Data Protector “virtual full backups.”
Application-based Disk Backup
Utilizing the file library functionality of backup applications is good for small or isolated jobs.
When a large-scale implementation is required, virtual tape offers a more easily managed, higher
performing solution. Consider a file library system if:
•The application is in a LAN or LAN/SAN hybrid configuration.
•Fewer than four servers write data to secondary disk storage.
•You can redeploy existing arrays as secondary disk storage.
•Your environment is static.
12 Concepts

Figure 3 Basic Write-to-disk Setup
Table 1 VLS Compared to Application-based Write-to-disk
Write-to-diskVirtual tape devices
Requires configuration of RAID groups, LUNs,
volumes, and file systems.
Sets up just like a physical tape library.Setup and
management
complexity
No device-side data compression available.Software or hardware enabled (software
compression generally decreases
performance).
Data compression
Performance dependent on target array or
server.
Hardware devices are tuned for sequential
read and write operations.
Performance
Free or licensed per TB in most backup
applications.
More expensive acquisition cost.
Backup software licenses as if physical library
or per TB.
Cost
Higher management overhead.
Storage efficiency gained through
compression.
Lower management overhead.
Business Copy
Using a business-copy solution (array snapshots/clones) generally involves a much higher cost
than a virtual library system. You might, however, implement such a solution if:
•Virtually instant recovery is critical.
•You need to leverage a high-availability investment.
•You are doing image recovery rather than file recovery.
•You need a zero downtime solution.
Disk-based Backup and Virtual Tape Libraries 13

Deduplication
Introduction
In recent years, the amount of data that companies produce has been steadily increasing. To
comply with government regulations, or simply for disaster recovery and archival purposes,
companies must retain more and more data. Consequently, the costs associated with data storage
– labor, power, cooling, floor space, transportation of physical media – have all risen. Virtual tape
libraries have become a cornerstone in modern data protection strategy due to their many benefits;
chief among these is cost. The list of virtual tape benefits also includes seamless integration into
existing backup solutions, improved SAN backup performance, and faster single file restores than
those performed with physical tape.
Deduplication, one of the most significant storage enhancements in recent years, promises to
reshape future data protection and disaster recovery solutions. This technology is ideal for virtual
tape libraries. Deduplication technology references blocks of data that have been previously stored,
and only stores new backup data that is unique. Data that is not unique is replaced with a pointer
to the location of the original data. Because there is often a great deal of duplicate data present
from one backup session to the next, disk space is consumed by similar or identical iterations of
data. Deduplication greatly improves storage efficiency by only storing an instance of data once,
while still allowing backup streams to be restored as if they had been retained in their entirety.
See Figure 4 (page 14).
Figure 4 Unique Backup Data
DescriptionItem
Data from the first backup stream is stored to disk.1
Duplicate data (in blue) as well as unique data (in red) in a second backup stream is identified.2
Duplicate data in the second backup stream is eliminated.3
Unique data in the second backup stream is stored to disk.4
HP Deduplication Solutions
HP offers two deduplication technologies: HP Accelerated deduplication, a licensed feature available
with HP Virtual Library Systems (VLS), and HP Dynamic deduplication, an integrated feature with
HP D2D Backup System. Both HP deduplication solutions offer the following benefits:
•Longer retention of data.
•Faster, less expensive recoveries and improved service levels.
•Fewer resources consumed, reducing operational costs.
•Completely transparent to host.
•No data is lost – backup streams can be fully restored.
•Block or chunk level deduplication, providing greater reduction of data.
•Even greater reduction of data when combined with traditional data compression.
14 Concepts

HP Accelerated deduplication and HP Dynamic deduplication are designed to meet different needs,
as shown in Table 2 (page 15).
Table 2 HP Deduplication Solutions
HP Dynamic deduplicationHP Accelerated deduplication
•Intended for mid-sized enterprise and remote office
users.
•Intended for enterprise users.
•Uses object-level differencing technology. •Uses hash-based chunking technology.
•Fastest possible backup performance. •Integrated deduplication.
•Fastest restores. •Lower cost and a smaller RAM footprint.
•Most scalable solution in terms of performance and
capacity. •Backup application and data type independence for
maximum flexibility.
•Potentially higher deduplication ratios.
See “Accelerated Deduplication” (page 87) for more details on the HP deduplication technology.
Deduplication Ratios
The storage capacity saved by deduplication is typically expressed as a ratio, where the sum of
all pre-deduplicated backup data is compared with the actual amount of storage the deduplicated
data requires. For example, a 10:1 ratio means that ten times more data is being stored than the
actual physical space it would require.
The most significant factors affecting the deduplication ratio are:
•How long the data is retained.
•How much the data changes between backups.
Table 3 (page 16) provides an example of storage savings achieved with deduplication. However,
many factors influence how much storage is saved in your specific environment. Based on the
retention policies shown below, six months of data without deduplication requires 12.75 TB of
disk space. With deduplication, six months of data requires less than 1.25 TB of storage.
Retention policy:
•1 week, 5 daily incremental backups
•6 months, 25 weekly full backups
Data parameters:
•Data compression rate = 2:1
•Daily change rate = 1% (10% of data in 10% of files)
Deduplication 15

Table 3 1 TB File Server Backup
Data stored with deduplicationData stored normally
500 GB500 GB1st daily full backup
5 GB50 GB1st daily incremental backup
5 GB50 GB2nd daily incremental backup
5 GB50 GB3rd daily incremental backup
5 GB50 GB4th daily incremental backup
5 GB50 GB5th daily incremental backup
25 GB500 GB2nd weekly full backup
25 GB500 GB3rd weekly full backup
...
25 GB500 GB25th weekly full backup
1,125 GB12,750 GBTotal
Approximately 11:1 reduction in data stored
Table 4 (page 16) is an example that may not reflect the savings that all environments achieve
using deduplication. As shown, deduplication ratios depend on the backup policy and on the
percentage of change between backups.
Table 4 Deduplication Ratio Impact
Backup policyDaily change
rate Daily incremental (10%) and weekly fullDaily full and weekly full
1 year6 months4 months*1 year6 months4 months*
23:116:112:125:119:115:10.5%
15:111:110:116:113:112:11.0%
9:17:17:19:19:18:12.0%
*4 months = 5 daily + 17 weekly backups
See “Performance” (page 94) for additional information on optimizing your deduplication
performance.
Target-based Deduplication
VLS and D2D deduplication is target-based; the process is running transparently inside the hardware.
This means that when the data is read (by copying to physical tape, restoring a backup, etc.), the
device rebuilds the data. The data that is read is identical to the data that was originally written
(like tape drive compression); there are no pointers in the read data.
Tape Oversubscription
Deduplication requires more virtual tape capacity than physical disk; this is sometimes called tape
oversubscription. The purpose of deduplication is to reduce the amount of disk required to store
multiple generations of backups. Be sure to create enough virtual tape capacity to contain your
entire retention policy, and the amount of physical disk will be much less capacity due to
deduplication.
For example, if you are backing up 50 TB per week and retaining four weeks, you need to create
enough virtual tape capacity (after compression) to store 200 TB of backups. If you have 2:1
16 Concepts

compression, you must create 100 TB of virtual tape capacity to hold the four weeks of backup
data. Given deduplication across the four weeks of backup versions, the amount of physical disk
required for this 100 TB of virtual tape would be significantly less.
NOTE: Do not create too much virtual tape capacity or your backup application may be set to
prefer to use blank tapes instead of recycling older tapes. You would likely run out of disk space
because the older backups are not being recycled/overwritten and thus the disk space used by
these old backups is not freed up. As in the example above, you should create enough virtual tape
capacity to hold backups for your entire retention policy but no more.
Replication
Introduction to Replication
Deduplication can automate the off-site process and enable disaster recovery by providing site to
site deduplication-enabled replication at a lower cost. Because deduplication knows what data
has changed at a block or byte level, replication becomes more intelligent and transfers only the
changed data instead of the complete data set. This saves time and replication bandwidth, and
is one of the most attractive features that deduplication offers. Replication enables better disaster
tolerance with higher reliability but without the operational costs associated with transporting data
off-site on physical tape.
You can take control of your data at its furthest outposts and bring it to the data center in a
cost-effective way. Using replication, you can protect data anywhere.
Figure 5 Enterprise Deployment with Small and Large Remote and Branch Offices
Replication provides end-to-end management of backup data from the small remote office to the
regional site and finally into the primary data center, all controlled from the primary data center,
while providing local access to backup data as well. Note that replication is within device families
(VLS to VLS, D2D to D2D).
HP Replication Solutions
Most companies now recognize the importance of a robust backup and restore data protection
strategy, although only enterprise level users tend to invest in site disaster recovery. In most cases,
data protection is in the form of daily off-siting of physical tapes. However, even the offsiting of
Replication 17

physical tapes has its down sides—a high level of manual intervention, tape tracking requirements,
etc. The physical transfer of tapes off-site is not very automated.
In addition, one of the pain points for many companies large and small is protecting data in remote
offices. Untrained IT staff manage a daily backup process involving changing of physical tapes,
and the process is prone to human error.
HP replication, available on its VLS and D2D systems, now offers the solution to both these problems.
You can replicate local backup data (virtual cartridges) between sites in a reliable, automated
manner at a fraction of the costs previously required when using high bandwidth links or in some
cases physical tape offsiting.
Consider the “Before” and “After” scenarios detailed below.
Figure 6 Remote Site Data Protection Before Replication
18 Concepts

Figure 7 Remote Site Data Protection Using Replication
Deduplication is the key technology enabler for replication on HP VLS and D2D systems. (VLS
systems use HP Accelerated deduplication, and D2D systems use Dynamic deduplication.) The
same technology that allows duplicate data to be detected and stored only once on the HP VLS or
D2D system also allows only the unique data to replicate between sites. Because the volume of
data being replicated between sites is much less than if the full data set was replicated, you can
use lower bandwidth links at correspondingly lower price points. In addition, backup at remote
offices can be automated to a local virtual tape library and then replicated back to a regional
data center or primary data center allowing end-to-end management from the data center of all
data in the remote offices.
This transformation is shown in Table 5 (page 19) which compares the amount of data to transfer
both with and without deduplication. The amount of data to back up in this example is 1 TB.
Table 5 Estimated Time to Replicate Data for a 1 TB Backup Environment at 2:1
Link Type
OC12T3T1Data Sent
622.1 Mb/s44.7 Mb/s1.5 Mb/sLink Rate (66% efficient)
Without deduplicationBackup Type
16 minutes3.8 hours4.5 days50 GBIncremental
2.7 hours1.6 days45.4 days500 GBFull
With deduplicationChange Rate
4.3 minutes59 minutes29 hours13.1 GB0.5%
5.3 minutes73 minutes35 hours16.3 GB1.0%
7.3 minutes102 minutes49 hours22.5 GB2.0%
Replication 19

NOTE: T1/T3 and OC12 are old terms with respect to WAN link terminology. Many link providers
use their own names (for example, IP Clear and Etherflow). This document distinguishes them by
their speed using 2 Mbits/sec, 50 Mbits/sec, etc.
One consideration with replication is that you must “initialize” the Virtual Tape Libraries with data
prior to starting the replication. This ensures that the source and target devices are both synchronized
with the relevant reference data to allow them to interpret the changed data (deltas) that comes
across the WAN link during replication.
Replication Deployment Options
You can deploy the HP VLS and D2D systems for replication in many ways depending on your
requirements. You should understand the terminology associated with deduplication and replication.
The key terminology for replication deployment:
•Source: A series of slots/cartridges in a virtual library that act as the source data to replicate.
This is the original copy of the backup data, written to and managed by the source site’s
backup application.
•Target or LAN/WAN destination: A series of corresponding slots in another virtual library on
another site in another location which receives data from the source library. This is the
secondary (disaster recovery) copy of the backup data, managed by the replication system.
For both HP VLS and D2D systems, the unit of replication is a virtual cartridge and the replication
link is TCP/IP (one GbE connection per node on the VLS system, and one to two GbE connections
on the D2D system). Figure 8 (page 21) shows how you can configure the system to replicate all
of the cartridges or just a subset of cartridges from the source virtual library to the target virtual
library.
20 Concepts