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
TM
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.
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