You mentioned a Compellent, which I presume to be a Compellent SAN. If you really want to dig into this, you'll need to work with the SAN team to map (using whatever terminology Compellent uses):

OS drive letters/mount points to LUNs

LUNs that are part of larger sets of LUNs (metaluns)

LUNs to RAIDsets (RAIDset: a collection of sets of storage bound together with a given RAID level)

RAIDsets to spindles (or SSD units)

And then you go back up the chain:

spindles to every RAIDset using each spindle

RAIDsets to LUNs

LUNs that are part of larger sets of LUNs (metaluns)

LUNs (metaluns) to the OS drive letters/mount points

After which exercise, you'll be able to see what your storage is shared with. Perhaps your LUNs each have spindles dedicated to them that do nothing else. Perhaps every single LUN you have is part of a storage pool that's shared with the Exchange email server, so heavy email traffic can slow down your database. Perhaps one or two of your LUNs is shared with a data warehousing box.

If you want to dig into storage performance, you must know the entire layout as it pertains to your system - otherwise, you can easily end up chasing phantoms caused by resources shared with other applications that have sporadic load cycles. Bottlenecks on the fiber channel connections are also possible, though less common.