MSCS Restrictions

[alanrenouf]

Hi,

One of the restrictions of MSCS is that it cannot be in a DRS or HA Cluster, does anyone know why this is the case ?

Page 16 - http://www.vmware.com/pdf/vi3_35/esx_3/r35u2/vi3_35_25_u2_mscs.pdf

I know it 'probably' will work but I need to know why it is not supported ?

If anyone can point me to a KB article or some VMware documentation to explain this I would be most grateful.

Thanks

Alan

[atbnet]

If you are using RDMs for example the quorum and data disks then you cant vmotion a VM. You could shutdown one cluster node and then cold migrate it.

Andy, VMware Certified Professional (VCP),

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[Yattong]

Hey Alan,

Its only supported when the boot drives of the nodes are on local VMFS datastores.

Also, when the VMkernel detects a bus sharing scsi controller, it will not allow vmotion.

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~y

[alanrenouf]

Yeah but I could just set the DRS rules on these specific hosts to disabled so they didnt VMotion, I can understand the Vmotion limitation but I dont get why they cant specifically be in a DRS or HA cluster ?!

Thanks for your input.

[alanrenouf]

Hi Yattong,

So are you saying it is supported in a HA DRS cluster, the doc says no ?!

Thanks

[Yattong · Accepted solution]

No Alan,

Its not supported in DRS/HA cluster. But like you said, if you do come across any issues, you can cold migrate the VM's to host thats not in a cluster to get support.

I believe when they say it shouldnt be a part of a DRS/HA cluster, is that I think they will assume DRS will be fully automated and the user doesnt know how to disable individual VM's.

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~y

[Yattong]

Have you read this thread?

http://communities.vmware.com/thread/141288

Just found it, and its basically what Ive said. Except the boot drive of the vm can now be on SAN, to allow HA.

But DRS still cannot vmotion anything with shared bus.

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~y

[alanrenouf]

No Alan,

Its not supported in DRS/HA cluster. But like you said, if you do come across any issues, you can cold migrate the VM's to host thats not in a cluster to get support.

I believe when they say it shouldnt be a part of a DRS/HA cluster, is that I think they will assume DRS will be fully automated and the user doesnt know how to disable individual VM's.

Thanks Yattong, totally agree, if only I could find a document to support this !

[alanrenouf]

Man I hate it when the formatting screws up ! :smileyangry:

[TomHowarth]

There you go Alan, I have edited the formating for you :smileygrin:

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Tom Howarth

VMware Communities User Moderator

[TomHowarth]

Hey Alan,

Its only supported when the boot drives of the nodes are on local VMFS datastores.

That is no longer the case, VMware now support MSCS where the System drives are on shared storage. I think the change came in at 3.5 U2

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Tom Howarth

VMware Communities User Moderator

[khavekost]

Alan, did you ever find a document to support your theory? I have folks balking at using HA and DRS on clusters hosting MSCS machines, even though we have it in production and everything is working fine - for about 8 months now. We have some folks who will not support an idea without it being totally supported by VMware documentation.

What did you find?

[VMmatty]

The documentation I have seen from VMware states that it still is not supported, even on vSphere. Check the following links:

VI3: http://www.vmware.com/pdf/vi3_35/esx_3/r35u2/vi3_35_25_u2_mscs.pdf

vSphere: http://www.vmware.com/pdf/vsphere4/r40/vsp_40_mscs.pdf