On Tue, 10 Mar 2009 09:21:54 -0700 (PDT), Wagg
wrote:

Possibly the wrong groups, but not too sure where to post this
question. A friend of mine has a Raid array, with three 146gb drives
in a compaq server, and then three 36gb drives, below that. The drives
were not re done, as the originals were the 36's, and they were just
swapped around in the cage they are in, the 146's up front at the top,
but the old ones at the bottom, still with the OS on them. The new
drives were configured as extra partitions.

Now my question is, with the 6 drives, between the partitioning and
setup (done by a professional company I am told) there is a missing
amount of 200gb between all the drives. Now I know that you loose a
certain amount with formatting and all that, but 200gb? Someone I know
who works in raids and just raids said that it doesnt appear to be
configured correctly, but without him seeing it (he doesn't live
anywhere near me or my other friend!) he cant be too sure, so I am
asking, does this sound right?

The company who set it up to begin with says the missing part is
normal, even up to that size. Just all seems a bit off to me.

What level of RAID is it? Different types "waste" different quantities
of space.

In this case, I'd guess from your figures that you have two RAID5
arrays of three drives each. RAID5 allows you to lose one disk in the
array without ill effect, and when you replace the failed disk the
array rebuilds back to fault-tolerant. It does this by using
equivalent space to one whole disk as "parity" error checking codes.

Boot array: 3x36, of which a third is used for parity.
Data array: 3x146, of which a third is used to parity.

So you have 146+36 gig "wasted" as parity, which is 182gig - quite
close to the 200gig you say.

Common RAID types:

RAID0 (or "not a RAID): 2x36gig disks, gives 2x36gig space as one
virtual disk, and no safety
RAID1 (mirror): 2x36gig disks, gives 1x36gig space as one virtual disk
and 1 disk fail tolerance
RAID5 (parity): Nx36gig disks, gives (N-1)x36gig space as one virtual
disk and 1 disk fail tolerance

Also,
JBOD (also "not a RAID", Just a Bunch of Disks): N disks of any sizes,
gives the combined sum of diskspace as one virtual disk with no
safety.

Cheers - Jaimie
--
I like nonsense. It wakes up the brain cells. -- Dr. Seuss