Check storage performance issues

[BertrandW]

Hello

CONFIGURATION

Hosts Configuration
- host3 (Dell R710, 8 CPU, 32GB RAM, no local HD)
- host4 (Dell 2920, 8 CPU, 16GB RAM, no local HD)
- host5 (Dell 2950, 8 CPU, 24GB RAM, 1.8TB Raid5 local HD)

all host are running ESXi 4.1.0 build 348481

SAN Configuration
- Dell 2950, 8 CPU, 8 GB RAM with
- PERC 5/i handling 3 virtual disk
        nb: 1/ and 2/ share same SAS HD
       - 1/ Windows 2008 R2 x64 running SanMelody : 2x 149GB SAS HD performing Raid1 30GB
       - 2/ iSCSI volume RAID1A  : 2x 149GB SAS HD performing Raid1 106GB
       - 3/ iSCSI volume RAID10C : 4x 1TB SATA HD performing Raid10 1.8TB
- PERC 6E attach to Dell enclosure MD1000 handling 4 virtual disk
       - 4/ iSCSI volume RAID10D : 4x 149GB SAS HD performing Raid10 272GB
       - 5/ iSCSI volume RAID10A : 4x 149GB SAS HD performing Raid10 272GB
       - 6/ iSCSI volume RAID10B : 4x 149GB SAS HD performing Raid10 272GB
       - 7/ iSCSI volume RAID1B  : 2x 250GB SATA HD performing Raid1 232GB

SAN offered 6 DATASTORE, reachable from any 3 hosts
 
SAN software is Datacore Sanmelody 3.0.4.2

Hosts (iSCSI) are configured with 1 active Gb vnic and 1 stand-by Gb vnic

SAN is configured with 1 Gb team (2 NIC)

We are using 2 netgear Gb switch non-manageable, no jumbo frame

3 hosts are running 19 virtual servers (EXCHANGE 2010, SQL 2005, DC, TMG, LYNC, SHAREPOINT, FILE SERVER, PRINT SERVER, ..)

PROBLEM

some vm are pretty slow sometimes, we can see there is high disk latency.
often we are under 50ms, but it happens to jump to 500ms, 1000ms, 4000ms and it seems there are no special activity at this moment.

What i have to do to check if our configuration is really correct ?

Thanks

[idle-jam]

esxtop will tell you more story of the performance issue. have a look here http://www.yellow-bricks.com/esxtop/

[jrenton]

I would guess that the performance issues you are experiencing are to do with your disk configurations.

From looking at the configuration I can see that each disk group you have setup contains a maximum of 4 disks.

Adding larger numbers of disks to each disk group will improve your storage performance.

You can then divide the disk group into LUNs to present as VMFS volumes in ESX.

You will also find that your SATA disk performance is much slower than SAS due to the seek speed on the disks.

[jrenton]

Anything over 50ms latency will cause you issues

See: http://www.vmware.com/files/pdf/scalable_storage_performance.pdf page 10.

The document will also help you to get the most performance from your storage.