Global Mirror of NetApp Image Mode Volumes
talor 27000411MV Visits (6423)
Recently I came across an interesting problem during a migration from NetApp storage, to a new V7000 Unified Storage System.
The migration from a block perspective was very straightforward. We used VMware VMotion to migrate from NetApp datastores to new V7000 block datastores, and we would then put the NetApp array behind the V7000 to perform image mode migrations.
This went as planned and all was good.
We were replicating using Global Mirror to another V7000 Unified storage system, so the next step was to create the auxiliary vdisks, and to then create the global mirror relationships, add them to a consistency group and kick off the replication. The problem was that when I was mirroring the vdisks which used to be NetApp volumes presented to Windows boxes that were migrated via image mode, the V7000 wouldn't allow the use of the auxiliary vdisks which had been created.
My college reminded me that NetApp calculate gigabytes using 1000xMiB, so to convert bytes to gigabytes the calculate 1024x1024x1000. IBM (and pretty well everyone else) use GiB calculating this via 1024x1024x1024.
The reason that my auxiliary volumes were no good was because they weren't exactly the same size!
What had to be done was to first work out the size of the NetApp volumes in bytes, for this we used the command line on the V7000:
Now that we knew the size of the primary volume in bytes, we just had to create the auxiliary volume in bytes on the DR V7000: