Best practice disk configuration for a Domain Controller VM

[paulmack]

Hello,

Microsoft best practice guides for a windows server domain controller says to use different physical disks for the OS and the active directory database to get the best performance. Does this kind of thing still apply when the DC is a VM? I'm thinking not. Anyone done any kind of testing or benchmarking in this kind of area or can give me some advise please?

There's points to be had here for some good info.

Thanks

Paul

[pdrace]

I don't think that it should be a factor on an ESX vm.

I don't see how you would gain any performance and it would seem quite wasteful to dedicate specific physical disks to the AD database unless you have storage with 9 or 18 GB drives.I would be surprised if you did. I have a stack of Seagate 9G Cheetahs in one of my desk drawers if you want them though.

The other consideration is that in a MS Virtual server VM the DC would share the hosts disks which is most likely not the case (shouldn't be) on ESX. This caveat is probably because you could have the HOST OS, the VM OS and the AD database perfroming I/O to the same physical disk or disks if you are using MS Virtual server.

[spex · Accepted solution]

Why not follow best practice in a virtual environment? Since you have (in a typical esx installation) some vmfs volumes on different san luns you can easily deploy an extra drive to your domain controllers. More important: have close look at your time synchronization, especially in an environment with physical dc's.

Regards

Spex

[paulmack]

Thanks for the input. Decided to go with seperate vmdk's in the end and store them on seperate LUNS and in the future possibly move them to RDM's.

Thanks

Paul

[jhanekom]

The same rule applies to a virtualised environment. Of course, in a SAN-based environment disk performance should outperform single spindles by an order of magnitude, so you can just place it on a different virtual disk (or, if you really insist, even on a different virtual disk on a different LUN), but this does not negate the reason for Microsoft's recommendation.

Windows Domain Dontrollers disable OS-based write caching on the volume containing the AD database. Therefore, if you store the AD database on the same volume as other data (say, your OS), you will take a performance hit.

For this reason, it is still a good practice to store the AD database on a separate volume. For the purposes of virtualisation, this volume can be just a separate virtual disk. (Note: placing it on a separate partition on the same virtual disk will not help.)