I've managed Dell's EMC and Equallogic SANs in the past. I was recently put in charge of a Hewlett-Packard P2000 SAN. HP and EMC use slightly different terminology. I'd like to confirm I understand HP's terminology. Can you verify/correct some of the definitions below?
vDisk. A collection of physical disks grouped into a RAID array. EMC refers to these as "Storage Pools." vDisks and Storage Pools aren't exactly the same as "RAID groups," but they serve the same purpose.
Volume. A logical division of a vDisk, which is presented to a host as a single volume. EMC refers to these as "LUNs", and LUN is the proper term.
Storage Groups. Distinct from "Storage Pools," EMC SANs can define "Storage Groups," which can combine multiple LUNs into a single volume that's presented to hosts. I can't find an equivalent to this on HP SANs.
Global Spares. Physical hard drives that are not assigned to any vDisk. If a hard drive in a vDisk fails, the SAN automatically uses an available spare to replace the drive and make the vDisk fault tolerant. EMC refers to these as "hot spares." With both vendors, spares do not need to be assigned to a particular RAID group or vDisk. The SAN will use them for any failed hard drive.
Regarding Equallogic SANs: Equallogic arrays create one RAID group and one LUN from all available disks in the array. The administrator can select only: the type of RAID in the RAID group, and the number and size of Storage Groups presented to the hosts.
I think I have these terms right, but I'd like to verify with someone who's used both vendors' SANs. I'm especially concerned that I can't find HP's equivalent of Storage Groups. Surely HP has a way to combine multiple LUNs into one logical volume. Am I missing that setting somewhere?