I recently came across a situation where a customer wanted to replicate volumes from their production Nimble Storage group to their secondary group at a Disaster Recovery (DR) site. Nothing unusual in that of course, it’s very straightforward to configure and a good percentage of Nimble customers replicate between disparate array groups. However, in this case the customer had implemented a scale out cluster at the DR site with 2 discreet storage pools configured, and they wanted to specify the target pool that a particular volume collection should be replicated into.
The first thing we should note is if the customer didn’t have any specific requirement to maintain separate pools at their DR site, then a simple solution would be to non-disruptively merge the pools to create a single destination pool for replication to DR. However the premise of this article is that in this instance, the customer wished to maintain separate pools in order to provide data segregation.
When a replication partnership is first configured on a group that contains more than one storage pool, the user is prompted to select the default destination pool for the incoming replicas to be stored. Once this default has been set, all volume collections replicated from the upstream partner will be placed into this pool.
So, what do we do if we want a particular volume collection to be replicated into another pool on the downstream group which isn’t the configured default?
Worry not, where there’s a will, there’s a way. On initial replication, the replica will always be created in the default destination pool as specified by the replication partnership. However, once replication has been established, it is possible to select the replica volume collection on the downstream array and initiate a move operation to migrate the replica to the desired destination pool. This starts a background data migration process to relocate the replica volume collection from the default pool to the newly specified pool. This operation doesn’t require incoming replication to be suspended, so replication from the upstream partner can continue throughout the move operation. Once the move is complete, you now have the downstream replica in the desired pool!
Tip: Don’t forget that for any scale out configuration it is mandatory to have Nimble Connection Manager (NCM) installed on all Windows and VMware hosts that will connect to the scale out group in order to support volume striping and non-disruptive volume moves.
It should also be noted that the Volume Move operation can be automated using API so can be readily scripted and automated if required.