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DX Object Storage: Remote Synchronize Writes Configuration

Introduction

The DX

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.

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.

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