Tuesday, March 20, 2012

Quorum & MSDTC Cluster Questions


We are trying to setup a Windows Server 2003 Cluster with 2 systems and a DAV. We intend to install SQL 2005 on this Cluster. We purchased a DAV with 3 physical disk arrays as follows.

73GB RAID 1 (our plan is to use this to store sql transaction logs)
146GB RAID 1 (sql backups, temp database & other temp files)
420GB RAID 10 (sql databases)

Now as we are setting all this up we find out we need a shared physical drive on the DAV to store the Quorom. It is my understanding we cannot partition the physical drives and use one of the partitions to store the Quorum because when you create the resource for the Quorum the resource is the phsyical disk not the partition.

So my question is, is it in our best interest to buy a seperate physical disk for the Quorom?

My next question is, with regards to the MSDTC, is it in our best interest to buy a seperate physical disk for the MSDTC or can we store it on the 146GB RAID 1 and still use the drive for its original purpose?

Any guidance is much appreciated.

- Nick

It's best to have each device on its own physical device, but this isn't required. Each does have to be its own partition (drive letter), though. Here's a white paper that goes into a lot more depth:

http://www.microsoft.com/downloads/details.aspx?FamilyID=818234dc-a17b-4f09-b282-c6830fead499&DisplayLang=en

Buck Woody

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Actually, the quorum does need to be in a different device than the database files, since it is part of a different cluster Resource Group. It needs to be able to fail over between the nodes independantly of the SQL service. Since the underlying SCSI protocols will attach an entire drive to one system or the other, you can't split partitions.

If your definition of DAV is the one I'm familiar with, you should verify that this storage can be used in a Windows cluster. My understanding is that clusters will only use SCSI, iSCSI, or SAN storage.

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That's a good point - when I said that it doesn't need to be on a separate device I should have been more clear. Many times clusters are set up on a SAN configuration. In that case you do want to present a separate LUN for the quorum drive, but you can use the same SAN/HBA. The whitepaper I have referenced there should help with the layout - if not, just re-post and we'll help out where we can.

Buck

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Thanks for your responses.

My apologies, I meant to say DAS not DAV. Sorry for the confusion.

It is a clusterable storage device that acts similarily to a SAN. We purchased it from DELL and they assured us it was certified to work in a Windows Cluster environment. Unfortunately for us we cannot split the drive arrays into multiple virtual drives. So we're stuck with 3 drive arrays and we cannot take one drive array and split it into 3 so the one drive array is presented to Windows as 3 seperate drives.

It does seem like a waste to have a seperate drive dedicated to the Quorum, especially since it only uses 4MB and the smallest HD you can find is 36GB.

What are your thoughts on Volume Mount Points? Does that work for the Quorum (or MS DTC for that matter)?

What about the MS DTC ? Does it need a seperate physical disk like the Quorum or can it be placed on drive with other minor usage?

Thanks again.

- Nick

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When I set up clustering we had this kind of layout:

C Drive: Physical, Local RAID 1, OS and Binaries

Q Drive: Physical, Local RAID 1, Quorum (yes, we cheated and put a few other things on here. But not much, and nothing that we let users get to)

S Drive: LUN, SAN, Shared DB Databases

L Drive: LUN, SAN, Shared DB Logs

I view this as the mininum, with other sets defined like S for high read/write activities and filegroups

Buck

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Thanks for your responses again.

Where did you place the MS DTC physical disk required by the SQL Cluster?

If you have a Cluster of 2 or more systems doesn't the Quorum drive have to be on a shared drive not local?

Thanks!

- Nick

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The issue isn't usage or volume of data. The issue is that the storage must be able to move from node to node independantly of any other resource group.

So, if you put MSDTC and the quorum on the same physical drive (even in separate partitions), then if you moved the cluster service from node A to node B, MSDTC would die because its disk would disappear out from under it. Worse, if MSDTC failed and took the disk offline, the cluster service would die.

For those reasons, MSCS won't let you configure two resource groups that depend on the same physical drive.

Can you give the model of the Dell array? That sounds interesting, and I'd like to read up on it. From your description, each array forms one virtual drive, but can't be divided into LUNs? That seems strange. With a device where you can form virtual disks (LUNs), you can set up a very small LUN for Quorum.

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Kevin

The DAS is a Dell PowerVault 220S DAS. Click here for more info.

The 2 servers we're setting this up on are "Dell 2950's running Server 2003 and SQL 2005".

We were going to arrange the drives like this:

On board *each* Dell PE2950:
(2) 73GB drives mirrored w/RAID 1 holding OS, Apps (C:) and Win Swap files (G:)

On DAS (220S):
Virtual Disk 0 - (2) 73GB drives mirrored w/RAID 1 for SQL Transaction Log files (D:)
Virtual Disk 1 - (2) 146 GB drives mirrored w/RAID 1 for a variety of temp jobs, SQL temp files, etc.(E:)
Virtual Disk 2 - (6) 146 GB drives mirrored and striped w/RAID 10 for the SQL database (F:)

We can't slice the paired drive sets using the SCSI controller as DELL disables 'slicing' virtual drives (sets) when you are in cluster config.

Thanks for your curiousity Kevin!

- Nick

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We're purchasing a 4th drive array for the DAS for the Quorum to reside. That said would it be wise to setup the clustering like this:

[Cluster Group]
Cluster IP Address
Cluster Name
SQL Network Name
SQL IP Address
SQL Server (With dependencies of Disk D:, E: & F:)
DTC Network Name
DTC IP Address
DTC Service (With dependencies of Disk E:)
Disk D: (Shared Drive, SQL Transaction Logs)
Disk E: (Shared Drive, SQL Temp Files, MS DTC)
Disk F: (Shared Drive, SQL Databases)
Disk Q: (Quorum)

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I think this looks good to me - you've got a C drive for local, obviously, so I'm assuming that's local to the system and a RAID 1 or similar.

Buck

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Almost.

Each Resource Group must be independant and not depend on any resource in any other group.

I'd lay it out as:

[Cluster Group]
Cluster IP Address
Cluster Name
Disk Q: (Quorum)

[SQL Group]

SQL Network Name
SQL IP Address
SQL Server (With dependencies of Disk D:, E: & F:)
Disk D: (Shared Drive, SQL Transaction Logs)
Disk E: (Shared Drive, SQL Temp Files)
Disk F: (Shared Drive, SQL Databases)

[DTC Group]


DTC Network Name
DTC IP Address
DTC Service (With dependencies of Disk G:)

Disk G:(DTC)

You could possibly combine SQL and DTC, but ideally they should be separate.


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