I'd like to start a discussion on a very important and general topic - the disk throughput rate on any of the ESX versions. The reason to do that is a design I'm working on including implementation of virtual file servers. What I bumped into during the test phase was very poor performance. What we tested - copying 1GB file from the virtual machine disks, and issueing time dd command with block size 1024 and count 1000000 from the console of the ESX. There are the results:

ESX 4 on BL460 – 20MB/s
SAN attached, 40MB/s local SAS disk. (SAN attachedis EVA)

ESX 4 on BL685c G5 –
15MB/s SAN attached, 20MB/s local SAS disks

From Virtual machine –
copying files on VMFS - 10MB/s

ESX 3.5 on BL685c G6 –
30MB/s on SAN and 20MB/s on local disks (SAN attached is Clariion)

ESX 4 on BL685c G6 –
30MB/s on SAN, 20MB/s on local SAS disks

From the virtual
machine copying 1GB file on VMFS datastore – about
25MB/s

From the virtual
machine copying 1GB file on RAW device – about
25MB/s

The numbers are not any
different when using LSI, BUS logic or Paravirtual bus. They also didn’t change
when the queue length extended to 128.

ESX 3.5 running on Dell
T300 test lab – about 25MB/s on local and iSCSI disks

I installed a clean Win
2003 enterprise server on a blade BL685c G6 on it’s local disks. Then presented
a disk from the same array and tested the performance – it was close to 500MB/s
…

I now start to wonder - is this typical for the ESX ? I've done many implementations so far but always with a dedicated VM team and never received complains. This time however I planned for file, application and DB servers on Virtual.. And now it seems like not such a good idea.

I would appreciate if you share some thoughts and maybe execute similar tests in your environments and paste the results here.

Thank you in advance