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VMware RDMs in standby VM node of MS SQL cluster -- primary node Physical

Posted on 2016-08-30
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I am trying to setup a Microsoft SQL 2012 cluster with one physical and one (standby) VM node. Physical Windows server node will access common storage using iSCSI initiator and the VM node will do so using RDM disks.

This is a supported configuration, but finer details are missing from VMware documentation:
http://pubs.vmware.com/vsphere-60/index.jsp#com.vmware.vsphere.mscs.doc/GUID-F984140C-B70B-4DFC-9E81-40615C67C950.html

When I put Windows server in the same SAN group on Dell Compellent iSCSI storage as VMware hosts, I got in big trouble because Windows server tried to access VMFS volumes, even though I kept them offline in Disk Management. All VMs went down one by one.

So I wish to know the safe way to deploy disks in this SQL cluster. The Windows server is now outside the SAN group but it needs to access the same 4 disks which are connected to standby VM node as RDMs. Will mapping those 4 volumes to both VMware Hosts Group and Windows server (not in that group) cause any issue? For the OS of the VM, I have used the standard VMFS volume, and all RDM disks have placed their VMDK files on the path of that VMFS volume, which concerns me. Should I use only RDM disks in the VM node, even for OS? Thanks.

AKulsh
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Question by:Akulsh
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Assisted Solution

by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 2000 total points
ID: 41777002
It sounds like you have got your iSCSI IQN (permissions) incorrect, of you have NO IQN permissions on LUNs.

each LUN, should have an IQN for an ESXi server so it can access it. On your VMFS datastores these LUNs should be excluded from your Physical Server.

on your Failover Cluster, these LUNs should have permissions for both physical and ESXi nodes which will access the LUNs directly for NTFS.

OS disks are usually VMDK, and RDM are Data disks.
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Author Comment

by:Akulsh
ID: 41777056
Andrew,

Thanks for quick response. Where do I specify these IQN permissions in Dell Compellent? I remember that it was easy to do in Dell EqualLogic. Thanks.

AK
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Author Comment

by:Akulsh
ID: 41778505
Let me add, I spoke to 2 Dell Compellent engineers and they informed that it cannot be done. In fact, one told me to use iSCSI initiator in VM to access the storage which makes no sense. There is a way to do it in Compellent by keeping Windows server outside the VMware cluster group, but Dell Support provided no assurance. I will be on my own.
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LVL 122
ID: 41778517
Oh! That would seem strange....

by iSCSI in a VM, they are referring to Software iSCSI initiator in the Guest VM, and you can build Failover Clusters that way.

But you would still have to be careful, because what Dell are stating is you CANNOT control permissions (Zone out) LUNs.
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Author Comment

by:Akulsh
ID: 41778648
I don't see how you can use "Software iSCSI initiator in the Guest VM" since for that to work, that VM must have NICs on the storage network, the way ESXi host do. How can this be done? Thanks.
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LVL 122
ID: 41778759
Create a virtual machine portgroup in the same network as the storage network.

e.g. add the virtual machine portgroup to the same vSwitch which connects to your storage network.

Post a new question, and we can discuss at length.
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Author Comment

by:Akulsh
ID: 41778793
But it will be no better than accessing RDM disks directly (without iSCSI initiator) -- as you yourself hinted earlier -- since that storage vSwitch is used by VMFS volumes.
I may or may not post a new question, but will update everyone if my sharing RDM volumes with Windows physical server from outside the Compellent 'server group' works. Thanks.
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LVL 122
ID: 41778859
RDM or Failover Cluster via Guest VM Software iSCSI have always been options for many years, when RDMs were not available.
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Expert Comment

by:compdigit44
ID: 41783945
I have a number of Windows cluster in our environment which use FC and/or FCoE. Any volume that will be used in the cluster I present as a RDM to one of the VM's then on the other click the option to use existing disk and assign the disk referenced in the other node. Of course SCSI bus sharing needs to be enabled.

I am a little confused as to your setup? Could you upload some screen shots
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Accepted Solution

by:
Akulsh earned 0 total points
ID: 41786561
compdigit44,

Perhaps you have cluster of only VMs. In my setup, there is one physical Windows server and one Windows VM and they need to share iSCSI disks of Compellent which does not permit IQN permission configuration.

In any case, I was able to make it work. See the 2 screen-shots enclosed. The 5 highlighted RDM disks are shared between two 'server' groups. Putting Windows node in the same 'server' group as VMware hosts had caused major problems.

 Thanks to all.
WorkingCompellentConfig-1.JPG
WorkingCompellentConfig-2.JPG
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LVL 122
ID: 41786639
We've never had any issues.
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Author Comment

by:Akulsh
ID: 41786647
Perhaps, in your storage you can configure IQN permissions.
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LVL 122
ID: 41786709
it does not make any difference provided you don't have dopey administrators, that Initialise and format a LUN! (RDM) presented to the VM.

Again good documentation, and trained Admins Helps.
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Assisted Solution

by:Akulsh
Akulsh earned 0 total points
ID: 41788650
I was finally able to install Windows Cluster. However, since VM node containing RDM disks does not use MPIO (Multi-Pathing) at OS level, the Cluster Validation Tool kept giving error. I could install SQL cluster only by using command line option "Setup /SkipRules=Cluster_VerifyForErrors" on both nodes. It seems to be healthy.

The VMware link given in my initial posting of this question is not only vague on many points, it is also wrong -- in my opinion -- in advising (1) not to use MPIO for either Physical or VM node, and (2) to use SCSI Bus Sharing, as if we are sharing disk between two VMs. Thanks.
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Author Closing Comment

by:Akulsh
ID: 41793921
My problem had to do with configuring Compellent storage correctly for sharing between a VM and a Physical server. Compellent Support does not want to answer questions on this topic, but the solution suggested by me is working.
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