storage area network - Differences between HP and EMC SAN

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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?

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class="normal">Answer

If this
P2000 is anything like my old MSA4400, then vDisks are volumes that are assigned to
servers as LUNs, but under the covers, what is happening on the HP has little in common
with a Clariion.

The way I remember it, the HP
has a bunch of disks that it sets up in fixed groups (with RAID, I think), and then
vDisks are created that live on these disks with their own virtual raid. So you could
have one vDisk with virtually raid 10, meaning each block or chunk that comprised the
vDisk would be saved twice, and another one with virtually raid 5, meaning that the
chunks would get saved once, but would have distributed
parity.

I'm a little hazy on the details about
the actual disks, whether there was raid under all these vDisks or just a JBOD. I do
remember that we had global spares, because we had several dozen disks of about 100 fail
over the course of three weeks, and the system was able to take the hits until more than
9 were rebuilding at the same time.

Maybe
someone with more recent and specific P2000 experience can chime in here and help, but
this is what I remember.