Re: Compaq Smart Array 3200 Controller as a SCSI Controller

[Paul Koning via cctalk]

> On Jul 17, 2020, at 2:54 PM, Grant Taylor via cctalk <cctalk@classiccmp.org> 
> wrote:
> 
> ..
>> Interesting. Is there an official RAID level for three drive parity?
> 
> I'm not aware of one.  But my ignorance thereof does not preclude it from 
> existing.

What is "three drive parity"?  "Parity" is the description of RAID-5, and 3 
drive RAID-5 is certainly perfectly standard.  RAID-1 is not parity, it's 
mirroring.  Is the question about triple mirroring, i.e., 3 drives all having 
the same data on them?  That's pretty rare though not unheard of, I've never 
seen a RAID-x designation for that.

For high availability, RAID-6 is much more economical (and at this point the 
standard choice); triple mirroring is of that class, with the difference that 
it performs better for random short writes.

        paul