vSphere 5.0 iSCSI Storage Issues

[TimTool]

Hi All,

This is my first post on the community so be kind,

I am having an issue with our ESX iSCSI environment and wondered if anyone could help. We have recently brought a IBM DS3524 iSCSI SAN with 1Gbps NIC. During IOMETER testing on a RAW partition the perfomance is as expected but when the same partition is formated it degrades - see pictures below

We have had a Contractor in to look at the envirmonment and he seems to think everything look ok, but could not understand the performance drop either.

Can anyone help?

Tim

[athlon_crazy]

Both pics show the same output?

[TimTool]

H,

Sorry i uploaded the wrong one by the looks of it - please see below:

The above image is the results of an IOMETER run on the same partition after NTFS format. This is using thick provision disks

[TimTool]

I have done abit more digging:

Running and ESXTOP while running IOMETER - with the U options on a RAW partition displays the following:

6225.39 - CMDS/s, 4053.88 - READS/s, WRITES/s - 2171.50, MBREAD/s - 31.67, MBWRITE/s - 16.96, DAVG/cmd -1.90

Running and ESXTOP while running IOMETER - with the U options on a FORMATTED partition displays the following:

487.08 - CMDS/s, 323.73 - READS/s, WRITES/s - 163.36, MBREAD/s - 2.64, MBWRITE/s - 1.27, DAVG/cmd - 7.01

The above partition is VMFS, with Thick Provisioned Eager Zero'd - MTFS Partition, thinking that it could be a VMFS \ VMWARE issue i have now attaced an physical server to the SAN using iSCSI and run the same tests - and the same poor results as with VMFS - see below

We have also tried changing the array from RAID 10 to 5 but there is no major differences between the performance.

[scottyyyc]

Perhaps try and hook up a target local workstation or server (non-virtual) as a simple secondary disk. Run the same tests, and that will at least tell you if it's something on the VMware side, or something on the SAN side. Quick and easy, seeing as Win7 and Server 08 have built in iSCSI initiators.

This sounds pretty peculiar, though, I would personally think it's something to do with the SAN. To be perfectly honest, even your non-NTFS formatted performance results seem really low (30MB/s Read, 16MB/s Write). For a Gig-E based iSCSI SAN without much running on it, you should be getting reasonably close to GigE speeds (100-110MB/s read/write). High 80's/90's at the minimum. I ran a couple quick tests on some EqualLogics I've had over the years, and even with lots of stuff running on it (40 VMs), I still get 80-100MB/s sustained read and write.

Also, I know IOMETER can be tricky to get proper results from. Perhaps try another benchhmarking tool to ensure you're not getting false positives. I use HDtach, as it's simple and free (although doesn't run under Vista/7/2008, XP/2003 only). At least then you know the results are valid. If it's slow across the board, I'd be getting on the phone with IBM.

[TimTool]

Hi scottyyyc,

Thankyou for your responce, i really appreciate it - so i have finally figured it out and it was a fundamental basic issue.

So it would seem that running IOMETER on a RAW partition was ok, but soon as it was formatted the results were skewed  - and this was down to Sophos AV scanning the created test file.

After creating adding an exclusion the tests results were as expected - now to figure out what other performance issues this is having with other files

Thanks

Tim