Compellent doesn't support Disk Spin-down. Not too sure what system specifically you are working with but I was able to find some info at the link below that lists out some of the specs and states that Drive spin-down is not an option.

www.evaluatorgroup.com/.../EGL1_Dell_Compellent.pdf

If you have any other questions please feel free to let me know.

I thought that this was the case (no disk spin down) but co-pilot support have tried to close our support incident with this as a reason.  The engineer claims that support has been added in a recent firmware version and cannot be turned off and this is a reason we see unexpected latency under low load.

Even if it were true it had been added in a recent version it would be amazing if this could not be turned off.

I would say if you are still having some latency issues, I would start a phone home and then contact Co-Pilot back and escalate the issue. That would be the fast way to get a resolution for your Compellent environment.

We have had this incident open for 4 months now with no resolution. Impressed, not!

James I sent you a direct email about the open case you are reffering to. Please reply when you get a moment.