[rescue] RAID (was Re: Insane drives)

[William W. Arnold]

Joshua D. Boyd writes ---
>On Tue, 10 Jul 2001, Robert Novak wrote:
>> If you have 10 9.1GB disks in your set, you get 75.6GB or so (assuming no
>> spares). Might want to use a hotspare if you have the capacity (Sun's
>> Disksuite will let you create a hotspare pool, so put one disk in it and
>> attach it to your RAID 5 metadevice).
>
>So, you are saying that you always only use one disk for parity?  I
>thought that was what raid 3 did.

Raid 3-5 all use 1 disk's worth of space for parity.

Raid 0: Striping
Raid 1: Mirriroring
Raid 2: Bit level ECC interleved through disks. (really rarely used)
Raid 3: 1 disk dedicated for parity. Parity calculated by the block/stripe,
        Disk heads defined to move in sync always. (Maximises large sequential
        Writes and Reads)
Raid 4: 1 disk dedicated for parity. Parity calculated by the block/stripe
        Heads allowed to be out of sync. (Parity disk becomes bottleneck for writes)
Raid 5: 1 disk worth of space for parity. Parity for each stripe is rotated
        through the disks.  Parity calculated by the block/stripe.

-- 
-billy- warnold at vipnet.org