Dell DX6000 User manual

DELL DX Object Storage
Platform –Remote
Synchronous Replication
Configuration
A Dell Technical White Paper
Dell
Storage Engineering

DX Object Storage: Remote Synchronize Writes Configuration
Page ii
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May 2010

DX Object Storage: Remote Synchronize Writes Configuration
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Contents
A Dell Technical White Paper .........................................................................................i
Dell .........................................................................................................................i
Storage Engineering .....................................................................................................i
Introduction ............................................................................................................. 2
Remote Synchronous Replication Overview ........................................................................ 2
Configuration of the Proxy ............................................................................................ 3
Additional References ................................................................................................. 5
Figures
Figure 1: Remote Synchronous Writes................................................................... 3
Figure 2: SCSP Proxy Configuration Console............................................................ 4
Figure 3: SCSP Proxy Adding Cluster Console........................................................... 5

DX Object Storage: Remote Synchronize Writes Configuration
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Introduction
The DX TM Object Storage Platform provides a mechanism for applications to write data to a local DX
Cluster and to replicate it over a standard IP network to a disaster recovery cluster synchronously,
within a single request. Unlike, remote asynchronous replication that is done through the Content
Router application, remote synchronous replication is not dependant on meta-data to identify streams
for replication. The application specifies that an object is to be replicated to a remote cluster at the
time of writing it to the local cluster. The object is written to both DX Clusters before a response is
sent back to the application. Since the object is replicated long distances over an IP network, there
may be performance aspects associated with remote synchronous writes that should be taken into
consideration. The purpose of this document is to provide DX Storage administrators, application
developers, and support teams instructions on the DX platform configuration required when
applications are utilizing the remote synchronous write feature to enable synchronous writes to a local
and remote DX Clusters.
Remote Synchronous Replication Overview
The DX Object Storage Platform allows an application to write or update objects on a local and remote
DX Clusters with one single operation. This is done by using the remote synchronous write
functionality. The Cluster Services Node (CSN) provides a SCSP Proxy interface to the DX Storage nodes
(SN). This interface accepts operations from applications and re-directs them to the DX Storage Nodes
in the designated cluster. It enables an application to interact with multiple DX Storage Clusters over a
secure WAN interface. An application can ensure that an object is written to the local cluster and then
immediately replicated to a disaster recovery DX Cluster, by writing the object to the local DX Cluster
through the proxy interface identifying the remote DX Cluster to which it should be replicated and
specifying that the replication should take place immediately.
When writing an object using remote synchronous writes, a single copy of the object is first written to
the local cluster. If the local write fails for any reason, an error response is returned to the requestor
and the operation is aborted. If the local write is successful, the SCSP Proxy will initiate a write to the
specified remote DX Cluster using the UUID assigned by the local DX Cluster. This request is
authenticated using the DX Storage administrator credentials specified in the configuration of the
remote DX Cluster in the SCSP Proxy. If the remote write is successful, a 201 Create response is
returned to the application indicating that the object was written successfully on both the local and
remote DX Clusters. If the remote write fails for any reason, a 202 Accept response is returned to that
application indicating that only the local write was successful. For cases when the local write succeeds
and the remote write fails, the application can rely on the remote replication occurring at a later time
using DX Content Router to convey the local stream to the remote cluster if that functionality is
enabled. Alternatively, the local copy can be deleted and the operation retried.

DX Object Storage: Remote Synchronize Writes Configuration
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Figure 1: Remote Synchronous Writes
CSN CSN
.
2. Write
Proxy
Application
3. Successful/
UUID Assigned
.
4. Write
with UUID
.
1. Remote Sync
Write Request
.
5. Write
Successful
.
6. Remote
Sync Write
Successul
Secure WAN / VPN Proxy
Configuration of the Proxy
The SCSP Proxy is capable of communicating with remote DX Cluster to enable replication between DX
Clusters and other supported remote methods that are described in the SCSP Proxy Overview
document. The proxy on the CSN is configured during the bootstrap process. In order to communicate
with remote DX Clusters, the DX Administrator must configure a list of remote DX Clusters on the CSN.
This can be done through the CSN web-based console under the Cluster Services->SCSP Proxy tab.

DX Object Storage: Remote Synchronize Writes Configuration
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Figure 2: SCSP Proxy Configuration Console
To add a remote DX Cluster to the configuration list, click the ‘Add Cluster’ button. To edit an existing
remote DX Cluster, click the ‘Edit’ button. To delete a DX Cluster from the list, click the checkbox in
the Delete column next to the DX Cluster that should be deleted and then click the ‘Update and
Restart’.
The following information is required for all remote clusters being configured:
Remote Cluster Name: The common name for a remote cluster that will be used in request sent to the
proxy. This name may not contain white spaces.
Host: The IP address or hostname of the remote proxy the local proxy will communicate with. The
host name may not contain whitespace.
Port: The port on which the remote proxy will listen to incoming requests. This is usually port 80.
User ID: The name of a DX Administrator that belongs to the DX Storage Administrators group for the
remote DX Cluster. This may not contain whitespace.
Password/Confirm Password: The password for the DX Administrator specified in the UserId field. This
option may contain spaces as long as they are not leading or trailing.

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Figure 3: SCSP Proxy Adding Cluster Console
Additional References
The following documents can be found on www.support.dell.com and can be referenced for additional
information on platform configuration required when utilizing the remote synchronous write feature to
enable synchronous writes to a local and remote DX Cluster.
Document
Description
Cluster Services Node Installation
and Configuration Guide
Provides information on configuration and administration tasks
for deploying and monitoring a DX Cluster Services Node.
DX Object Storage Application
Guide
Guides application programmers who are developing or
customizing client-side programs.
SCSP Proxy Overview
Provides an overview of the SCSP proxy and covers the steps for
configuring and running the proxy.