Ask, and be very specific, what your SAN admin means by "disk".

Remember, you have, in some ordering (ask your SAN admin)

Physical spindles/SSD's

RAID groups

LUNs

MetaLUNs (sets of LUNs in a RAID)

For SQL Server performance, you need to know, at a minimum:

1) Which parts of which physical spindles/SSDs does each of your drive letters/mount points map to?

2) What else maps to those physical spindles/SSDs?