biokovo
Enthusiast
Enthusiast

Advice about raw disk

We have a few Linux+Oracle servers on Blade servers and MSA SAS storage.

I have never used a raw disk, and I am thinking to try it on this servers.

Is it any IO improvemant?

How to add a raw disk (I have no option (gray?!) to add raw disk in VM settings->Add disk...)?

Thanks

0 Kudos
5 Replies
jamesbowling
VMware Employee
VMware Employee

From what I have seen, there isn't a huge difference in performance. I imagine it is really a personal choice. Do you already have a LUN carved out for the RDM? Is it already being presented to the host?

If you found this at all helpful please award points by using the correct or helpful buttons! Thanks!

James B. | Blog: http://www.vSential.com | Twitter: @vSential --- If you found this helpful then please awards helpful or correct points accordingly. Thanks!
Rich123
Enthusiast
Enthusiast

Take a look here:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=101770...

Like James said, you need to have the storage carved out and presented first.

Rich

biokovo
Enthusiast
Enthusiast

Thanks. The problem was because option RdmFilter.HbaShared in host software advanced settings was checked, now is ok.

Is there any reason not to use the RDM?

If I will not use snapshoot is it better physical or virtual mode of raw disk?

0 Kudos
jamesbowling
VMware Employee
VMware Employee

Do you plan on ever needing to vMotion the VM anywhere? If so, I believe you need to use Virtual Mode.

If you found this at all helpful please award points by using the correct or helpful buttons! Thanks!

James B. | Blog: http://www.vSential.com | Twitter: @vSential --- If you found this helpful then please awards helpful or correct points accordingly. Thanks!
0 Kudos
Rich123
Enthusiast
Enthusiast

I have a few VMs that use RDM (physical). I can vMotion them. I can't snap them without shutting them down. As you've said, if you don't plan to snapshot, that may not be a big deal for you. I've found people get hooked on being able to snapshot because it gives a warm feeling of comfort that you can easily undue something that's gone wrong (if you have a snapshot).

vmware provides reasons to use RDMs as:

- If you plan to use VMs that will be in a Microsoft cluster

- If you plan to use SAN snapshots that needto see the raw storage

- If you plan to have big files

I'm actually looking at getting rid of my RDMs because of a backup solution we're considering. Vmware consolidated backup (VCB) ignores them and that's not what I'm looking for. I haven't been able to find a reason not to use them since the above three don't apply to me. If they don't apply to you either, I would stick with a virtual disk.

Rich

0 Kudos