VM live migration between hosts with dif storage config

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DANILO MONTAGNA

Well-Known Member
Jun 28, 2019
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Hi,

I have a cluster with 4 nodes, 2 access one iscsi storage and other 2 access a dif storage, the storage A is only shared betwen host A and B, storage B is only shared between host C and host D, this is because they are in dif sites connected by fiber channel network, each site has a storage node...

Question: How can I online migrate one VM from Host A to Host C if they are not accessing the same storage resource?... This migration must be online.... I tried over CLI, using "--with-local-disks --online" but it didn't work because the volumes between nodes cant have the same STORAGE NAME in the cluster...

I know that I could just attach the Storage B volume to Host A and live migrate but it will require some networking changes and vlan cross-over between these two sites that we are trying to avoid at this moment!!!

The storage connection on each site is using LVM over ISCSI ..
 
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Hi,
this kind of setup is currently not supported for migrations. If you have the shared flag set on a storage, PVE migration expects the storage to be available on the target node. We'd need to refine the check to cover such cases as well, I created an entry in the bug tracker.

This means you cannot use a storage with shared 1 for migration when that storage is not available on the target.

A different workaround to the one you mentioned is moving the volumes of the VM to a different storage and live migrate afterwards (there is also the --targetstorage option if the storages are named differently on A and C). I suggest testing this approach on a dummy VM first, to make sure it works as expected.
 
Even with targetstorage option.. after the command is entered the CLI says it started the migration.. but nothing happens afterwards.

I think this behavior can be easily treated, the shared flag doesn't means it MUST be shared between all cluster nodes... it should read the "nodes list" selection into storage mount at Datacenter Level and flag the shared option only for those nodes, hosts not listed for that volume mount should thus be treated as non-shared, working similar to "VMware Storage Vmotion" feature..
 
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DANILO MONTAGNA said:
Even with targetstorage option.. after the command is entered the CLI says it started the migration.. but nothing happens afterwards.
Click to expand...
Yes, that's why I said you need to move it to a different storage that is not marked as shared (or marked as shared and available on the target), before using the targetstorage option.

DANILO MONTAGNA said:
I think this behavior can be easily treated, the shared flag doesn't means it MUST be shared between all cluster nodes... it should read the "nodes list" selection into storage mount at Datacenter Level and flag the shared option only for those nodes, hosts not listed for that volume mount should thus be treated as non-shared, working similar to "VMware Storage Vmotion" feature..
Click to expand...
It's certainly possible to implement. But the surrounding code is rather complex/aged historically, so there is some work required making sure nothing breaks. But currently shared 1 means "available on target" in the context of migration. That's why I created the entry in the bug tracker.
 
Thanks Fabian...

I'll follow this bug tracker in order to see if any improvement on this request was made to allow this kind of storage migration!!

Regards,
 
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