I'm new to this VM thing so here goes.
We have just recently finished virtualizing our entire data center. We are having a big performance problem with our Exchange sever in particular. Since the migration, we have been experiencing a lot of latencey using Outlook. I ran the Exchange troubleshooting assistant and it is saying that there is a bottleneck in the disk I/O. Any thoughts on what can be done to improve this issue?
All of the servers are on their own LUN, the RAID array is RAID 6.
HOw many HBAs do you have per host? Have spread the load across all available paths to storage? I assume you have installed VMware tools in your VMs -
HBAs are the storage adapters you are using to connect to your SAN - the output of ESXCFG-INFO should have that info -
We are using a Storevault S500 with 3.3TB of storage. We migrated our exchange server from a dual 2.GHzProcessors, 2GB RAM, everything installed locally on the physical server. We have about 200 users working on excahnge.
OK. How the storage is connected to the VM? Is it RDM or virtual disk stored on the Storevault?
How many drives, which Raid level and what type of disks (seems to be SATA) are used for the Exchange LUN?
Hmm, 15SAS drives should be enough for 200 Exchange users. Is the array's performance otherwise acceptable? For example cloning a VM stored on the array could roughly show the performance. You can start the cloning, go to the console, type "esxtop", then press "d" to display the current throughput (the 2 columns on right).
Also, as the storage connection is iSCSI, there might be lots of obstacles on the path. Maybe first try pinging the array's portal IP address from ESX console to verify the basic connectivity and latency for the iSCSI path. You can try the command "vmkping -c 100 IPADDRESS" for it.
You can also ask for help your storage service provider (or reseller), there might some known problem with the array's firmware, the Raid6 or some specific settings. Eg. chunksize.
Did you perform any performance testing on the array before placing the Exchange on it? I can send you an IOmeter test definition to benchmark the perfomance.
Nothing bad on the CPU/MEM side.
Do you have dedicated switches for your iSCSI SAN?
Could you screen shot the output of esxtop showing network and disk?
hit N and D keys to get those outputs.
Did you convert your Exchange from a physical server to a virtual server or did you do a reinstallation?
Assuming that you converted the server, what OS was it running. There have been some issues with conversion of physical server with more than 1 cpu in Windows 2000, resulting in poor performance because the converted server was only using 1 vCPU, but had a multiprocessor HAL (you can verify this in the device manager, look for uniprocesser acpi or multi processer acpi)
How many servers is running on the storage system? Is Exchange the only one with a problem?
I am using a iSCSI with a Storevault S500 and 12 SATA disks over RAID-DP (sorta like RAID6). I have an Exchange VM with 300 email users and experience no problems whatsoever. I have 6 other VMs on the same SAN device as well.
What do your performance statistics show on your Storevault device through the management software (web interface). There's a section that shows you disk read/writes and gives you an idea how much disk usage is going on.