[Performance] Datastore Virtual Disk or Raw Device LUN

[perfectid]

We are trying to find out the fastest solution for one of our internal systems.

Currently we have a datastore which is located at a iSCSI SAN via a virtualdisk file.

Since we want to benefit the maximum out of the configuration of de iSCSI SAN, we want to know which solution is faster:

- Via datastore as virtual disk (diskfile)

- Via direct LUN mappingl (RAW mapping)

I've been searching the documents, but cannot find any figures/numbers how much performance gain we would be able to get.

We are not using snapshots (and are not going to use then as well), and what other pinpoints should I also consider while making the decision for changing the architechture?

[mcowger]

Performance is basically equivalent between RDM and VMDK/VMFS (shown numerous times via whitepapers, etc).

You should use whatever works for your management needs. Basically, fi you need to weird SAN stuff (array level snapshots, replication, etc) you should use a RAW mode RDM. pretty much anything use VMFS.

--Matt

VCP, vExpert, Unix Geek

[perfectid]

Thanks for your quick reply!

It's quite simple, we need the best performance.

I've read several whitepapers too, however I didn't see a proper load test described anywhere to 'prove' what solutions is the fastest.

But as I read your post properly, you say we won't benefit changing from the vmk files to the raw lun mappings?

We will adjust our management policy accordingly when we know which solution is performance wise the best to choose.

The solutions that's deployed now has been installed by a 3rd party, and we want to investigate if we can make any improvements regarding diskperformance to it.

[mcowger · Accepted solution]

There may be performance improvements you can make in your env, but they wont come from switching from VMDK to RDM.

--Matt

VCP, vExpert, Unix Geek

[perfectid]

OK, thats a clear answer , thanks!

Can you push me in the right direction where (in a basic setup) I would be able to get some performance gain.

I'm not using VMware ESXi for a long time yet, but I'm willing do dive into it to get the maximum performance out of the setup.

You don't have to explain the full solutions (rather not), so I can do some research myself, but I'm missing the keywords where I should concentrate myself at.

Thanks in advance!

[DSTAVERT]

The only thing that provides real information is testing using your setup. Don't forget that you can also use the iSCS disks directly within the guest OS.

[AlbertWT]

Hi,

I've tried to test iSCSI connection using Windows Server 2003 x64 Std Edition and it doesn't seems to be workingwith that guest OS.

perhaps i need to use the enterprise Edition ?

Kind Regards,

AWT