VMware storage migration with virtual mode RDM - insufficient space

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michealo

[H]ard|Gawd
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I posted this on the VMware community forums and even opened a support case to no avail.
Hoping someone here has experienced this before and i'm not crazy





We're having trouble storage migrating a VM that has a 36GB thin provisioned VMDK disk and (2) 1TB virtual mode independent-persistent RDMs (fiber LUNs).
Virtual disk format is same as source, we're not trying to change the format of any of the disks during the migration.

The destination datastore has ~700GB of free space but vSphere/Web client both tell us that there is insufficient space for the RDM disks to proceed when clicking 'finish'.
We swear we've done this before and the RDM total capacity was not taken into account and only the VMDK disk size mattered.

Is this incorrect or has something changed in vSphere 5.5?
Perhaps another issue we're not remembering?
 
I think you need to do an advanced migrate

right click migrate

change datastore

advanced

the two RDMs keep at current location

select new LUN to migrate VMDKs to

next

finish


Hope this helps.....
 
thanks, i did find a blog article yesterday that mentioned performing the storage migration in two steps, first move the VMDK disk to new datastore then move the RDM's but i still get the same "insufficient space" error on the latter.
this also left the VM straddled between two datastores and we want to migrate off of the former.

unfortunately, we don't have any < 5.5 clusters left to test our theory that this worked fine in the past.
VMware support actually called me back a bit ago with info that they are looking into this, when at first they indicated this was never possible.
of course we could power off the VM, detach the RDM's, migrate the VM to new datastore and reattach the RDMs but as we all know, downtime is the 'real' issue here.
 
in case anyone else comes across this issue, it's related to datastore cluster miscalculating the RDM capacity.

recreating the datastore cluster did not help but dragging datastores out of the cluster for the VM storage migration to succeed then dragging them back in is an easy workaround.
 
Thanks for the follow-up on this. Is there a VMware KB on it? And what version are you running?


And why would you use virtual-mode RDM's in the first place?
 
5.5 revision 2143827 currently.
no KB, VMware support is still researching if this is restricted to just our cluster (very possible) and haven't been able to reproduce elsewhere.

we need virtual mode RDMs primarily for our backup solution (netbackup snapshots) and only use physical mode RDMs for VMs that require it (SAN appliances and MS clustering).
 
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