Windows dynamic disk for backup repositories?

[ekranz]

Here is our layout. We are running Veeam on a physical windows server. The disk we use for our backup repositories is a dedicated fiber connected SAN. The SAN is limited to a max lun size of 2TB. We have roughly 60TB that we want to use as repository space.

One thought we had is to assign 2TB LUNs to the server, and use windows dynamic disks to create a few larger disks.

What would be the best practice in a situation like this?

[Gostev]

Hi Ed, I see nothing wrong with your idea.

[JoshF]

Hi Ed,

We do this successfully with around 20TB, only we're doing this to work around VMWare 4.1 disk size limitations. Is obviously additional management overhead during provisioning/deprovisioning, however iometer/iozone seemed to believe that when using 32/64k blocksizes, this JBOD configuration outperformed the Windows Software RAID1 configuration of same (using to concatenate LUNs to singe volume.

Hope this helps

[ekranz]

Thanks Gostev and Josh.

My two main concerns were performance and management/recoverability. I am planning on documenting each LUN and which dynamic disk it is a part of in case of hardware issues with the backup server, or if we ever decide to move these disks to another server. It's my understanding that the configuration information of a dynamic disk is held within the disk itself, and you just need to make sure that all parts of a disk are available to the new server if moving.

[Gostev]

Frankly, I have never done this myself (attaching dynamic disk to another server). I too assume there will be no issues, however it would definitely be a good idea to test the process before implementing.

[bsousapt]

Hi Ed,

Based on my experiences and knowledge , i don't see any added value to use a dynamic disk for your situation.
If you want to create a mirror , dynamic, disk within your Windows Server by using multiple LUNS from your SAN, than it might be worthwhile...However i don't recommend this approach in terms of management/DR.
I would suggest to assign multiple LUNS from your SAN to the windows server, and use multiple drive letters as backup repositories, or instead of creating a dynamic disk create a GPT basic disk.
As far as i know starting Win2003 SP1 and XP x64 bits the limits for a disk is :

maximum raw partition of 18 exabytes (Windows file systems currently are limited to 256 terabytes each.)

However since your SAN limits a LUN size to 2TB you don't need this as well, so my suggestion is to keep it as simple as possible, and in this case means using multiple basic disks.
Assuming you could use 18 disks (18 drive letters) you could make use of 36TB as repository target, and assuming a very conservative deduplication factor of 2:1 we already talk about 72TB of data to store

As a side note i have created many times dynamic disks, and i was , so far, always able to detach it from one server and attach to other servers without any problems.

Good luck, and if you need something , let us know

[averylarry]

I didn't think a backup repository could span multiple drive letters . . ?

[Gostev]

Correct, however a volume can span multiple disks...

[averylarry]

Right. I was just refuting what bsousapt said. Or at least what I understood from this:

. . . keep it as simple as possible, and in this case means using multiple basic disks.
Assuming you could use 18 disks (18 drive letters) you could make use of 36TB as repository target, and assuming a very conservative deduplication factor of 2:1 we already talk about 72TB of data to store . . .

Unless DFS is being used, which I wouldn't think is "simple" by any means.

[bsousapt]

I didn't think a backup repository could span multiple drive letters . . ?

You´re correct,however you can have multiple backup repositories.
See this an a example :

• - 6 disks of 2TB each(20TB total) , using drive letters e,f,g,h,i,j

• - 6 backup repositories , 1 for Windows VM's backup daily, 1 for Linux VM´s backup daily , 1 for Monthy Win VM's backup, 1 for Monthly Linux VM´s, 1 for Yearly Win VM´s and 1 for Yearly Linux VM´s

With such approach you avoid added complexity of DFS and dynamic disks and you gain, to my opinion, flexibility to deal with your current backup requirements and future ones.
As a side note it helps to create several jobs based on the type of OS used by the VM's, for instance to assure VSS and non-VSS backups.

Bruno