vSphere 7 automatic VMs (vCLS) in SRM placeholder volume

[komanek]

Hello,

I recently migrated my 2 sites to VCSA 7.0u1d (due to some 3rd party software not supported on 7.0u2 yet). There is also SRM 8.3.1 installed. Among VCSA 7's new features are automatic virtual machines for cluster services, named "vCLS (n)" where "n" is a sequence number. In my case, they were placed to SRM's placeholder volumes and there seems to be no configuration option to tell them not to use these volumes. After I migrate these virtual machines with Storage vMotion to a different volume, they are destroyed and recreated again in the placeholder volume with incremented sequence numbers in their names.

Is it a problem for SRM to have these running machines placed on placeholder volumes? If so, how can I prevent this from happening?

Thanks in advance for clarification.

Best regards,

  David

[Daniel_Georgiev]

Hi,

according to the documentation and my observation, this should not be a problem for SRM. 

How Site Recovery Manager Interacts with vSphere Cluster Services:

The vCLS agent virtual machines cannot be stored on a replicated datastore managed by Site Recovery Manager. You must have a non-replicated datastore with a minimum free capacity of 6 GB.

About Placeholder Virtual Machines:

The files of the placeholder virtual machines are very small, and do not represent full copies of the protected virtual machines. The placeholder virtual machine does not have any disks attached to it. The placeholder virtual machine reserves compute resources on the recovery site, and provides the location in the vCenter Server inventory to which the protected virtual machine recovers when you run recovery.

If you want to disable vCLS, you can refer to this KB - https://kb.vmware.com/s/article/80472

Hope this helps,

Daniel G.

[komanek]

Hi,

thank you for the answer. Does it mean, that SRM is not affected by using the placeholder volume by other activities? My primary concern was that the placeholder volume should be considered as dedicated to SRM. Hopefully, that is not the case. On the other hand, I have no problem to create an extra non-replicated volume for vCLS instances, but it seems to me there is no guarantee these virtual machines will end up there for residency. As far as SRM 8.3.1 has been declared to be compatible with vCenter 7.0u1, I probably do not need to worry about, but still, I'd like to be sure. SRM is expensive, so it would rather do it's job when needed 🙂

David

[Daniel_Georgiev · Accepted solution]

Yes, unless you don't disconnect\break the placeholder datastore with these other activities, you can use that datastore with other VMs. The datastore selection for vCLS VMS is selected based on all datastore ranking, you can see find more info in this doc - Datastore selection for vCLS VMs 

Excerpt from the doc for placeholder VMs. (Link):

The files of the placeholder virtual machines are very small, and do not represent full copies of the protected virtual machines. The placeholder virtual machine does not have any disks attached to it. The placeholder virtual machine reserves compute resources on the recovery site, and provides the location in the vCenter Server inventory to which the protected virtual machine recovers when you run recovery.

There is one new feature implemented in SRM 8.4 for Automatic Placeholder Datastore Selection which can help you - Automatic Placeholder Datastore Selection 

Hope this help,

Daniel G.

[komanek]

Hi,

thank you very much for the explanation. I'm now happy with the vCLS feature, regarding the info you gave me 🙂

Regards,

  David