Poor disk performances on a SBS 2008 vm under ESXI 4.1

[itpassionate77]

Hi all,

I come back with a question about vmdk files locations and best practices.

With my colleague a big discussion raised about vmdk locations for a vm that will run an heavy SBS 2008 installation. Where to place vmdk files on datastore and how to optimize them to get the best performances.

Here is the context. We've recently bought a ML350 G6 server with 2*RAID1 SAS 10k. We've installed ESXI 4.1 on the first RAID1 array (datastore1) and on the second RAID1 array we've created datastore2.

On this ESXI server we've created a VM SBS2K8. And here's come the discussion:

We've configured the vitual HDD for this VM as follow:

DATASTORE1:

Beside ESXI installation we've created 1st vmdk where we've installed OS partition for VM SBS2K8

DATASTORE2:

We've created the 2nd vmdk where we've installed the DATA partition for VM SBS2K8

For your information, directly after the installation we've moved Exchange database and log files on the second partition on DATASTORE2

Everything was nice during the installation of the vm, also during the setup of SBS 2008. The problems came just after the finishing of importation of pst files in the Exchange Database (+/- 20GB for all pst together).

The VM is so slow when we try to copy, backup files locally. I've checked the performances' charts in VSphere Client when we copied files or backup. The latency at disk, datastore, virtual disks level exploded.

It was at a point that the console became completely unresponsive during peaks...

My opinion on this, is that it would be better to put 2 vmdk's for the VM on DATASTORE2, but maybe I'm wrong. That's why I post this here as we're new.

All recommendations, advices, are welcome. I don't know if the problem is coming from the design of the VM itself or we forgot something during the setup.

Is there a good litterature about vmdk's files? Location, design,...

Thanks all for your help on this,

Michaël

[a_p_ · Accepted solution]

This sounds as if you bought the DL350 G6 with the P410i controller but no BBWC/FBWC attached for write-back operation. Without BBWC/FBWC you will usually see less  than ~10-20MB/s.

Placing the OS and data partition on different datastores in this case makes no difference at all.

André

[J1mbo]

As said already the write cache is needed.  Then reconfigure the box with a four-drive raid-10 instead.

[itpassionate77]

Hello André,

You were correct, we've bought the BBWC/FBWC and now, the performances are really nice.

Regarding all documentation I've read on the net. I think the best option is to simply install ESXI on USB stick or on SSD and, if we use the local storage of the server to host the VM, put 2 vmdks of the same vm on the same array.

My conclusion on this is, when you use RAID controller of a server to host VM think about the Memory module. This is very important!

Good learn!

thanks for your help on this