IBM Netfinity ServeRAID-3H User manual

IBM
IBM Netfinity
ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L
Ultra2 SCSI Controllers
Installation and User's Guide

IBM IBM Netfinity
ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L
Ultra2 SCSI Controllers
Installation and User's Guide

Note
Before using this information and the product it supports, be sure to read the general information under
Appendix A, “Product warranties and notices” on page 115.
Third Edition (December 1999)
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This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information
herein; these changes will be incorporated in new editions of the publication. IBM may make improvements and/or changes in the
product(s) and/or the program(s) described in this publication at any time.
This publication was developed for products and services offered in the United States of America and the United Kingdom. It is
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Copyright International Business Machines Corporation 1996, 1999. All rights reserved.
Note to U.S. Government Users — Documentation related to restricted rights — Use, duplication or disclosure is subject to
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Contents
About this section ................................................ v
How this book is organized ............................................ v
Notices used in this book ............................................. vi
Chapter 1. Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Option package contents ............................................. 2
Installation overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Understanding RAID technology ......................................... 4
Stripe-unit size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Supported RAID levels ............................................. 4
Chapter 2. Installing and cabling a ServeRAID controller ........................ 11
Controller features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Connector locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Installing the ServeRAID controller ........................................ 15
Connecting external devices ........................................... 16
Chapter 3. Configuring controllers using the ServeRAID Manager program ............ 17
Using the ServeRAID Manager program interface ............................... 17
Using the ServeRAID Manager program in bootable-CD mode ....................... 19
Starting the ServeRAID Manager program .................................. 19
Using the Configuration mode ......................................... 21
Using the Information mode .......................................... 28
Using the ServeRAID Manager program installed on your system ..................... 29
Starting the ServeRAID Manager program after installing your operating system ........... 29
Configuring the ServeRAID controller .................................... 31
Using the Notification Manager ........................................ 34
Using the Security Manager .......................................... 36
Setting user preferences ............................................ 37
Understanding drive states ............................................ 38
Physical drive state descriptions ....................................... 38
Logical drive state descriptions ........................................ 38
Configuring two ServeRAID controllers in a failover environment (Windows NT 4.0 only) ........ 39
Hardware requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Installation guidelines, considerations, and restrictions ........................... 40
Preparing the controllers for failover configuration ............................. 40
Configuring the controllers for failover .................................... 43
Connecting the expansion enclosures .................................... 44
Configuring logical drives ............................................ 44
Setting merge group numbers ......................................... 45
Completing the failover environment installation .............................. 45
Chapter 4. Installing device drivers and utility programs ........................ 47
Obtaining ServeRAID updates .......................................... 48
Installing ServeRAID device drivers ....................................... 49
Installing device drivers for Windows NT ................................... 49
Installing the files for Windows NT 3.5 .................................... 49
Installing the files for Windows NT 4.0 .................................... 50
Installing device drivers for NetWare ..................................... 51
Installing device drivers for Linux 2.2.x (or later) .............................. 53
Copyright IBM Corp. 1996, 1999 iii

Installing device drivers for OS/2 ....................................... 55
Installing device drivers for OpenServer ................................... 58
Installing device drivers for UnixWare .................................... 60
Installing the ServeRAID Manager program .................................. 64
Installing on Windows NT, Windows 98, or Windows 95 .......................... 64
Installing on NetWare .............................................. 64
Installing on OS/2 ................................................ 66
Installing on UnixWare ............................................. 66
Installing the IPSSEND and IPSMON command-line programs ....................... 67
Installing IPSSEND and IPSMON for Windows NT, NetWare, or OS/2 ................. 68
Installing IPSSEND and IPSMON for Linux ................................. 69
Installing IPSSEND and IPSMON for OpenServer ............................. 69
Installing IPSSEND and IPSMON for UnixWare .............................. 70
Installing IPSSEND for IBM DOS ....................................... 70
Chapter 5. Using utility programs ...................................... 73
Using FlashMan, the IBM ServeRAID ROM Update program ........................ 74
Using the ServeRAID Mini-Configuration program ............................... 74
Viewing the controller status .......................................... 75
Viewing the configuration ............................................ 76
Using the advanced configuration functions ................................. 76
Running the IPSSEND program ......................................... 78
Using the IPSSEND program ........................................... 78
FlashCopy function (for Windows NT only) ................................. 78
Server roll-out functions ............................................ 84
Error-recovery functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Problem-isolation and debug commands ................................... 88
RAID Configuration commands ........................................ 90
Starting the IPSMON program .......................................... 92
Using the IPSMON program ........................................... 92
Chapter 6. Solving ServeRAID problems .................................. 95
ServeRAID controller messages ......................................... 96
ServeRAID startup messages ......................................... 96
ServeRAID POST messages ........................................ 100
ServeRAID ISPR, BCS, and ECS POST error codes .......................... 101
Rebuilding a defunct drive ............................................ 105
Steps for recovering from defunct drives .................................. 106
Rebuilding a hot-swap drive ......................................... 106
Recovering from an incomplete format of a physical drive ......................... 106
Recovering from a failure in a failover-environment ............................. 107
Replacing a non-hot-plug controller in a failover pair ............................ 107
Chapter 7. Getting help, service, and information ............................ 109
Before you call for service ............................................ 109
Getting customer support and service ..................................... 109
Using electronic support services ...................................... 109
Using the World Wide Web ......................................... 110
Getting information by fax .......................................... 110
Getting help online .............................................. 110
Getting help by telephone .......................................... 111
Getting help around the world ........................................ 112
Purchasing additional services ......................................... 112
900-Number operating system and hardware support line ........................ 112
iv IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

Network and server support line ...................................... 112
Ordering support line services ........................................ 113
Warranty and repair services ........................................ 113
Ordering publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Appendix A. Product warranties and notices .............................. 115
Warranty Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
IBM Statement of Limited Warranty for United States, Puerto Rico, and Canada (Part 1 - General
Terms) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
IBM Statement of Warranty Worldwide except Canada, Puerto Rico, Turkey, United States (Part 1
- General Terms) .............................................. 117
Part 2 - Worldwide Country-Unique Terms ................................ 119
Notices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Year 2000 readiness and instructions ................................... 122
Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
United Kingdom telecommunications safety requirement ........................ 124
European community directive conformance statement ......................... 124
Industry Canada Class A Emission Compliance Statement ....................... 124
Australia and New Zealand Class A Statement .............................. 124
Taiwanese electromagnetic interference (EMI) statement ........................ 125
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
Contents v

Before installing this product, read the Safety Information.
Antes de instalar este produto, leia as Informações de Segurança.
Před instalací tohoto produktu si přečtěte příručku bezpečnostních instrukcí.
Læs sikkerhedsforskrifterne, før du installerer dette produkt.
Ennen kuin asennat tämän tuotteen, lue turvaohjeet kohdasta Safety Information.
Avant d'installer ce produit, lisez les consignes de sécurité.
Vor der Installation dieses Produkts die Sicherheitshinweise lesen.
Prima di installare questo prodotto, leggere le Informazioni sulla Sicurezza
Lees voordat u dit product installeert eerst de veiligheidsvoorschriften.
Les sikkerhetsinformasjonen (Safety Information) før du installerer dette produktet.
Antes de instalar este produto, leia as Informações sobre Segurança.
Pred inštaláciou tohto zariadenia si pečítaje Bezpečnostné predpisy.
Antes de instalar este producto lea la información de seguridad.
Läs säkerhetsinformationen innan du installerar den här produkten.
vi IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

About this section
This section provides information needed for configuring an IBMNetfinityServeRAIDcontroller and
instructions for installing and using the ServeRAID utility programs.
Note: The IBM ServeRAID product can be either a controller on an adapter, such as the one in this
option package, or a controller on the system board of your server. For consistency in this
manual, the ServeRAID product is referred to as a ServeRAID controller, unless it is specifically
noted otherwise.
To install device drivers and utility programs for an IBM ServeRAID controller that comes as a
standard feature on an IBM Netfinity or PC Server system board, see the installation instructions
and CDs provided with your server for instructions.
How this book is organized
Chapter 1, “Getting started,”contains introductory information about the IBM ServeRAID-3H,
ServeRAID-3HB and ServeRAID-3L controllers, a content listing for the ServeRAID option package, an
installation overview, and general information about RAID technology.
Chapter 2, “Installing and cabling a ServeRAID controller,”provides information about the standard
features of the ServeRAID-3H, ServeRAID-3HB and ServeRAID-3L controllers, and instructions for
installing and cabling a ServeRAID controller that is on an adapter.
Chapter 3, “Configuring controllers using the ServeRAID Manager program,”explains how to use the IBM
ServeRAID Manager program to configure one or more devices attached to a ServeRAID controller. You
can use the ServeRAID Manager program in two ways:
In bootable-CD mode (on the IBM ServeRAID Support CD), to configure your ServeRAID controller
before you install the device drivers and operating system. This includes configuring two ServeRAID
controllers in a failover environment.
Installed on your system, to configure, administer, and monitor your ServeRAID controller.
You can install the ServeRAID Manager program on systems running MicrosoftWindows95, Windows
98, Windows NT, Novell NetWare, IBMOS/2, or SCO UnixWare.
Chapter 4, “Installing device drivers and utility programs,”contains the instructions needed to install the
ServeRAID device drivers and programs provided on the IBM ServeRAID Support CD and diskettes that
come with the ServeRAID controllers.
Chapter 5, “Using utility programs,”contains instructions for starting using the IBM FlashMan program, the
IBM ServeRAID Mini-Configuration program, and the IPSSEND and IPSMON command-line programs.
You can use these operating-system specific programs to maintain and monitor your ServeRAID
subsystem.
Chapter 6, “Solving ServeRAID problems,”describes the ServeRAID POST error codes and startup
messages. This chapter also includes some basic information about rebuilding a defunct drive.
Chapter 7, “Getting help, service, and information,”provides information about accessing the IBM
HelpCenter, and World Wide Web sites to obtain future code and updates for the ServeRAID controllers.
Appendix A, “Product warranties and notices,”contains warranty information, product notices, and
trademarks.
Copyright IBM Corp. 1996, 1999 vii

Notices used in this book
This book contains notices to highlight information as follows:
Notes:
These notices provide important tips, guidance, or advice.
Attention:
These notices indicate possible damage to programs, devices, or data. An attention notice is placed
just before the instruction or situation in which damage could occur.
viii IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

Chapter 1. Getting started
This book provides the information needed to install and configure an IBM ServeRAID ServeRAID-3H,
ServeRAID-3HB, or ServeRAID-3L. These high-performance, redundant array of independent disk (RAID)
controllers are ideally suited for data-storage environments that require superior performance, flexibility,
and reliable data storage.
You also can use the configuration and reference information in this book to configure the IBM ServeRAID
controllers provided on some IBM Netfinity and PC Server system boards.
This chapter contains:
Option package contents ............................................. 2
Installation overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Understanding RAID technology ......................................... 4
Stripe-unit size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Supported RAID levels ............................................. 4
Understanding RAID level-0 ........................................ 5
Understanding RAID Level-1 ........................................ 6
Understanding RAID Level-1 Enhanced ................................. 7
Understanding RAID Level-5 ........................................ 8
Understanding RAID Level-5 Enhanced ................................. 9
Selecting a RAID level and performance tuning ............................. 10
Copyright IBM Corp. 1996, 1999 1

Option package contents
In addition to this book, the ServeRAID option package contains:
IBM Netfinity ServeRAID-3L Ultra2 SCSI Controller or
IBM Netfinity ServeRAID-3H Ultra2 SCSI Controller or
IBM Netfinity ServeRAID-3HB Ultra2 SCSI Controller with battery-backup write cache.
Attention:
Do not open the static-protective bag containing the controller until you are instructed to do so.
IBM ServeRAID support package:
–IBM ServeRAID Support CD
–IBM ServeRAID Device Driver Diskette
–IBM ServeRAID Device Drivers for SCO Operating Systems Diskette
See Chapter 3, “Configuring controllers using the ServeRAID Manager program”on page 17 and
Chapter 4, “Installing device drivers and utility programs”on page 47 for more detailed information.
IBM ServeRAID Channel 3 Cable option kit
This cable comes with the ServeRAID-3H and ServeRAID-3HB controllers only. You can attach this
cable to the ServeRAID-3H controller or the ServeRAID-3HB controller to convert the internal SCSI
channel connector to an external connector. See “ServeRAID-3H and ServeRAID-3HB controller”on
page 13 for more information.
Contact your place of purchase if any items are missing or damaged.
2IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

Installation overview
This book contains reference, configuration, and administration information for the IBM ServeRAID
controllers. In addition to this book, you might need to refer to your IBM server documentation for safety
information, connector locations, and for controller and hard-disk-drive installation instructions.
Note: The IBM ServeRAID product can be either a controller on an adapter, such as the one in this
option package, or a controller that is built-in on the system board of your server. For consistency
in this manual, the ServeRAID product is referred to as a ServeRAID controller, unless it is
specifically noted otherwise.
The information that you will need to install or configure your IBM ServeRAID subsystem depends on the
type of ServeRAID controller you are using and your familiarity with RAID technology.
A typical installation and configuration of an IBM ServeRAID subsystem consists of the following steps:
1Learning about RAID technology.
The “Understanding RAID technology”section in this chapter contains general information about
RAID technology. If you already are familiar with the IBM implementation of RAID technology, you
might want to start your installation with step 2.
2Installing the ServeRAID-3H, ServeRAID-3HB or ServeRAID-3L controller.
Chapter 2, “Installing and cabling a ServeRAID controller”provides information about the standard
features of the ServeRAID-3H, ServeRAID-3HB and ServeRAID-3L controllers, and installation and
cabling instructions for the controllers. You will not need the information in this chapter if you are
using a ServeRAID controller on an IBM Netfinity or PC Server system board.
3Updating your BIOS and firmware on your ServeRAID controller to the latest levels.
“Using FlashMan, the IBM ServeRAID ROM Update program”on page 74 explains how to quickly
and easily check the level of BIOS and firmware on your ServeRAID controllers. This program also
updates the BIOS and firmware for you.
4Using the ServeRAID Manager program to configure your disk array.
Chapter 3, “Configuring controllers using the ServeRAID Manager program”explains how to use the
IBM ServeRAID Manager program. You can refer to the information in this chapter or the online
help in the programs when configuring one or more devices attached to a ServeRAID controller.
5Installing your ServeRAID device drivers, operating system, and ServeRAID utility programs.
You can skip this step if you are installing multiple ServeRAID controllers and you already installed
your operating system and the most current versions of the ServeRAID device drivers and utility
programs.
To install these files for a ServeRAID-3H, ServeRAID-3HB or a ServeRAID-3L, see the
information provided with your operating system and Chapter 4, “Installing device drivers and
utility programs”on page 47 for instructions.
After you install the device drivers, refer to Chapter 3, “Configuring controllers using the ServeRAID
Manager program”on page 17.
Chapter 1. Getting started 3

Understanding RAID technology
RAID is the technology of grouping several physical drives in a computer into an array that you can define
as one or more logical drives. Each logical drive appears to the operating system as a single drive. This
grouping technique greatly enhances logical-drive capacity and performance beyond the physical
limitations of a single physical drive.
When you group multiple physical drives into a logical drive, the ServeRAID controller can transfer data in
parallel from the multiple drives in the array. This parallel transfer yields data-transfer rates that are many
times higher than with nonarrayed drives. This increased speed makes the system better able to meet the
throughput (the amount of work in a given amount of time) or productivity needs of the multiple-user
network environment.
The ability to respond to multiple data requests provides not only an impressive increase in throughput,
but also a decrease in response time. The combination of parallel transfers and simultaneous responses
to multiple requests allows disk arrays to provide a high level of performance in network environments.
Stripe-unit size
With RAID technology, data is striped across an array of physical drives. This data-distribution scheme
complements the way the operating system requests data.
The granularity at which data is stored on one drive of the array before subsequent data is stored on the
next drive of the array is called the stripe-unit size.
You can control the stripe-unit size and maximize the performance of your ServeRAID controller by setting
a stripe-unit size to a value that is close to the size of the system I/O requests. You can set the stripe-unit
size to 8 KB, 16 KB, 32 KB, or 64 KB. For example, performance in transaction-based environments,
which typically involve large blocks of data, might be optimal when the stripe-unit size is set to 32 KB or
64 KB; however, performance in file and print environments, which typically involve multiple small blocks
of data, might be optimal when the stripe-unit size is set to 8 KB or 16 KB.
The collection, in logical order of these stripe units, from the first drive of the array to the last drive of the
array, is called a stripe.
Note: If you are using the ServeRAID-3L:
Eight physical drives are supported in an array if the stripe-unit size is set to 32 KB or 64 KB.
Sixteen physical drives are supported in an array if the stripe-unit size is set to 8 KB or 16 KB.
If you are using the ServeRAID-3H or ServeRAID-3HB, sixteen physical drives are supported in an
array if the stripe-unit size is set to 32 KB or 64 KB.
Supported RAID levels
Disk arrays are used to improve performance and reliability. The amount of improvement depends on the
application programs that you run on the server and the RAID levels that you assign to the logical drives.
The ServeRAID controllers support RAID level-0, RAID level-1, RAID level-1 Enhanced (1E), RAID level-5
and RAID level-5 Enhanced (5E).
4IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

Understanding RAID level-0
RAID level-0 stripes the data across all the drives in the array. This offers substantial speed
enhancement, but provides for no data redundancy. RAID level-0 provides the largest capacity of the
RAID levels offered, because no room is taken up for redundant data or data-parity storage.
RAID level-0 requires a minimum of one drive and, depending upon the level of firmware and the
stripe-unit size, supports a maximum of eight or 16 drives.
The following illustration shows an example of a RAID level-0 logical drive.
You start with two physical drives.
Create an array using the two physical drives.
Then, create a logical drive within that array.
The data is striped across the drives, creating blocks.
Notice that the data is striped across all the drives in the
array, but no redundant data is stored. 1 2
3 4
5 6
7 8
A physical drive failure within the array results in loss of data in the logical drive assigned RAID level-0,
but only in that logical drive. If you have logical drives assigned RAID level-1, 1E, 5, or 5E in the same
array, they will not lose data.
Note: You can assign RAID level-0 only to logical drives in an array that contains only one physical drive.
When you replace a failed drive, the ServeRAID controller can rebuild all the RAID level-1E and RAID
level-5E logical drives automatically onto the replacement physical drive. However, any data stored in a
failed RAID level-0 logical drive is lost.
Chapter 1. Getting started 5

Though the risk of data loss is present, you might want to assign RAID level-0 to one of the logical drives
to take advantage of the speed offered with this RAID level. You could use this logical drive to enter data
that you back up each day and for which safety is not of primary importance, that is, data that you can
re-create easily. You also might want to use a RAID level-0 logical drive when the work you are doing
requires maximum capacity.
Understanding RAID Level-1
RAID level-1 provides 100% data redundancy and requires only two physical drives. With RAID level-1,
the first half of a stripe is the original data; the second half of a stripe is a mirror (that is, a copy) of the
data, but written to the other drive in the RAID level-1 array.
Because the data is mirrored, the capacity of the logical drive when assigned RAID level-1 is 50% of the
array capacity.
The following illustration shows an example of a RAID level-1 logical drive.
You start with two physical drives.
Create an array using the two physical drives.
Then, create a logical drive within that array.
The data is striped across the drives, creating blocks.
Notice that the data on the drive on the right is a mirror
copy of the drive on the left. 1 1
2 2
3 3
4 4
With RAID level-1, if one of the physical drives fails, the ServeRAID controller switches read and write
requests to the remaining functional drive in the RAID level-1 array.
6IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

Understanding RAID Level-1 Enhanced
If you have three or more physical drives in the array, you can no longer select RAID level-1, but you can
select RAID level-1 Enhanced (also called RAID level-1E).
RAID level-1E combines mirroring with data striping. This RAID level stripes data and copies of the data
across all of the drives in the array. As with the standard RAID level-1, the data is mirrored, and the
capacity of the logical drive is 50% of the array capacity of the grouping of physical drives in the array.
RAID level-1E requires a minimum of three drives and, depending upon the level of firmware and the
stripe-unit size, supports a maximum of eight or 16 drives.
The following illustration is an example of an Enhanced RAID level-1 logical drive.
You start with three physical drives.
Create an array using the physical drives.
Then, create a logical drive within that array.
The data is striped across the drives, creating blocks.
Notice that the stripe labeled *is the data stripe and the
stripe labeled **is the mirror (that is, the copy) of the
preceding data stripe. Also notice that each block on the
mirror stripe is shifted one drive.
1 2 3
3 1 2
4 5 6
6 4 5
x*
*
*
*
*
*
With RAID level-1E, if one of the physical drives fails, the ServeRAID controller switches read and write
requests to the remaining functional drives in the RAID level-1E array.
Chapter 1. Getting started 7

Understanding RAID Level-5
RAID level-5 requires a minimum of three physical drives. This RAID level stripes data and parity across
all drives in the array. When an array is assigned RAID level-5, the capacity of the array is reduced by
one drive (for data-parity storage).
RAID level-5 is generally the most desirable choice, because it offers both data protection and increased
throughput. RAID level-5 gives you higher capacity than RAID level-1, but RAID level-1 offers better
performance.
The RAID level-5 requires a minimum of three drives and, depending upon the level of firmware and the
stripe-unit size, supports a maximum of eight or 16 drives.
The following illustration is an example of a RAID level-5 logical drive.
You start with four physical drives.
x
Create an array using three of the physical drives,
leaving the fourth as a hot-spare drive.
x
Then, create a logical drive within that array.
x
The data is striped across the drives, creating blocks.
Notice that the storage of the data parity (denoted by *)
also is striped, and it shifts from drive to drive.
A parity block (*) contains a representation of the data
from the other blocks in the same stripe. x*
**
3 4
1 2
*
5 6
7 8
8IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers

If a physical drive fails in the array, the ServeRAID
controller switches read and write requests to the
remaining functional drive in the RAID level-5 array,
which is a hot-spare drive.
x**
**
2 1
3 4
5 6
8 7
Understanding RAID Level-5 Enhanced
RAID level-5 Enhanced (also called RAID level-5E) requires a minimum of four physical drives. RAID
level-5E is also firmware-specific. You can think of RAID level-5E as "RAID level-5 with a built-in spare
drive."
Reading from and writing to four disk drives is more efficient than three disk drives and an idle hot spare
and therefore improves performance. Additionally, the spare drive is actually part of the RAID level-5E
array, as shown in the following example. With such a configuration, you cannot share the spare drive
with other arrays. If you want a spare drive for any other array, you must have another spare drive for
those arrays.
Like RAID level-5, this RAID level stripes data and parity across all of the drives in the array. When an
array is assigned RAID level-5E, the capacity of the logical drive is reduced by the capacity of two
physical drives in the array (that is, one for parity and one for the spare).
RAID level-5E is a very desirable choice, because it offers both data protection and increased throughput,
in addition to the built-in spare drive.
Note: For RAID level-5E, you can have only one logical drive in an array. When using RAID level-5E,
you can have a maximum of seven logical drives on the controller.
RAID level-5E requires a minimum of four drives and, depending upon the level of firmware and the
stripe-unit size, supports a maximum of eight or 16 drives.
The following illustration is an example of a RAID level-5E logical drive.
You start with four physical drives.
x
Create an array using all four physical drives.
Chapter 1. Getting started 9

Then, create a logical drive (labeled as 1) within the
array.
Notice that the distributed spare drive is the free space
(labeled as 2) below the logical drive. x
1
2
The data is striped across the drives, creating blocks in
the logical drive.
The storage of the data parity (denoted by *) is striped,
and it shifts from drive to drive as it does in RAID
level-5.
Notice that the spare drive is not striped.
x**
7 8 9
*
1 2 3
4 5 6
If a physical drive fails in the array, the data from the
failed drive is compressed into the distributed spare
drive. The logical drive remains RAID level-5E.
When you replace the failed drive, the data for the
logical drive decompresses and returns to the original
striping scheme. x**
3 4
1 2
*
5 6
*
9*
7 8
Note: The ServeRAID Manager program Express configuration does not default to RAID level-5E. If you
have four physical drives, Express configuration defaults to RAID level-5 with a hot-spare drive.
Selecting a RAID level and performance tuning
When selecting a RAID level for your system, consider the following:
RAID level Data
Redundancy Hard Disk Drive Capacity
Utilization
Read
Performance Write Performance Built-in Spare Drive
RAID level-0 No 100% Excellent Excellent No
RAID level-1 Yes 50% Very Good Very Good No
RAID level-1E Yes 50% Very Good Very Good No
RAID level-5 Yes 67% to 94%1Excellent2Good2No
RAID level-5E Yes 50% to 88%1Excellent2Good2Yes
1Depending on the number of physical drives in the array.
2Performance depends on the number of drives in the array. Generally, the more drives in the array, the better your performance.
10 IBM ServeRAID-3H, ServeRAID-3HB, and ServeRAID-3L, Controllers