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Dynamic Mirrored Quorum Disk

Created: 17 May 2011 • Updated: 14 Jul 2011 | 3 comments
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Hi Everyone - another question about Dynamic Mirrored Quorum Disks on SFW & campus clusters:

I understand the procedure for setting up MS Failover Cluster on SFW is to first establish the Microsoft Failover cluster, then install SFW. After installing SFW, I can create a dynamic mirrored quorum disk.

It seems to me that I would need to reserve a "temporary quorum" volume on an array first; as the MS Failover Cluster will not function without a quorum disk. After that, I can use two other volumes (one on each array, or four if following recommendations) to create my dynamic mirrored quorum, switch the MS Cluster Quorum Resource to the SFW dynamic mirrored quorum volume, and then remove the initial "temporary" quorum disk.


1. Create temporary basic disk quorum volume on array

2. Set up MS Failover Cluster, with basic quorum disk.

3. Install SFW

4. Create SFW dynamic mirrored quorum from 2 additional volumes (one on each array)

5. Switch MS Failover Cluster quorum resource from basic disk (temp volume) to SFW dynamic mirrored quorum resource.

6. The temporary basic disk quorum volume on the array can be deleted.

My questions:

1. In practice, do I really need a temporary basic disk quorum followed by a dynamic one? Is there a way to re-use the temporary basic disk quorum as one half of the dynamic mirrored quorum, or will I have to ask my SAN team to configure a total of 3 volumes and then delete one of them after I'm done with the set-up?

2. I read that the quorum should have drive letter Q:, if Q: is in use by the basic quorum when I configure the dynamic quorum volume, how can I make sure that the dynamic quorum disk will have drive letter Q:?


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Wally_Heim's picture

Hi Danielk1981,

Windows 2008 Failover Cluster can be configured without a Witness disk (also known as quorum in earlier versions of Windows.)  You do not need to have a temporary disk for this function.  If you want to configure a Witness disk until after SFW is installed then you can go right to a Clustered Dynamic Diskgroup.

As for the drive letter, most people put the quorum or Witness disk to the Q: drive as a standard.  Windows Failover Cluster does not require a specific drive letter for the quorum or witness disk.



David Honeycutt's picture

Hi DanielK1981,

Short answer: no, it's always better to go with the Best Practice, it keeps us out of some major pitfalls. The steps you outlined above should be used to configure the online Windows Failover Cluster.

Regarding your wish to use the drive letter Q:, some switching need to be done, follow the steps below:

1. move the Quorum from basic Q: volume to dynamic disk volume (e.g. O:\)

2. remove the basic disk from the Cluster and remove the Q: drive letter from the volume (frees up the letter)

3. add the old basic disk that previously hosted the Q:\ and add it to the dynamic disk group where the new Quorum volume is now located and create a new volume on it (e.g. DynamicQuorum with Q:\)

4. move the Quorum to the Q:\

5. remove the O:\ volume and disk from above DG

6. verify the disk and request the correct disk to be removed by the SAN Admin

David Honeycutt

David Honeycutt's picture

Hi DanielK1981,

Wally is right about Windows Failover Cluster on 2008. My reference is focused on Windows Server 2003 Clustering.

Which version is your question for?

David Honeycutt