Understanding Performance counters

[SteveD03]

I'm auditing a firm for the first time. I want to view the storage performace for a specific datastore and the VMs. The client has 9 SQL servers on only one datastore volume. (Talk about putting your eggs in one basket) I can't log in via the CLI because I only have view rights to the GUI.

First off, do I read the datastore of a VM or the disk in the Advanced section of the performance tab? What am I looking for in terms of poor performance besides high I/O? What level of latency determines high I/O 15 MS? They have a iSCSI SAN too.

[mittim12]

Each application is different but storage IO control by default doesn't kick in until 30 ms so I always feel that's a good place to start.     Also look for anything being queued.

[iw123]

Hi,

This article might be worth a look. http://myvirtualcloud.net/?p=949

It's a shame you don't have CLI access otherwise esxtop or vscsistats could be used.

[SteveD03]

Thanks, that link was very helpful!

[mittim12]

This blog will be wortwhile too. 

http://blogs.vmware.com/vsphere/2012/06/troubleshooting-storage-performance-in-vsphere-part-2.html

[SteveD03]

That link was good too. It helped me make a good observation. The one thing that I have not been able to find the difference is between the datastore and disk counters. Anyone?

[mcowger · Accepted solution]

There are separate counters because a datastore != disk.  A datastore can be a single LUN, a combo of multiple LUNs (extents) or a network connection (NFS).