SATA PT2

[Jeremy Fowler]

RAID 0 is a striped set, no parity.
RAID 1 is a mirrored set.

So RAID60 would be two RAID 6 arrays striped together.

RAID61 would be two mirrored RAID 6 arrays... I could see maybe why you
would strip two RAID 6 arrays to increase performance, but that would be
incredibly costly and I would say complete overkill.  If you need redundancy
and speed is a high priority, you might as well do RAID10, a stripped set of
mirrored drives. However, if you a have a limited number of drives and
needed the most storage size by reducing the ratio of parity drives and disk
I/O performance isn't too important then RAID 5/6 is your answer.

On 6/5/07, Phil Thayer <phil.thayer at vitalsite.com> wrote:
>
> If you do that you need to make sure that the controller will support
> RAID 6 or RAID ADG.  This is simply a RAID 5 with an additional parity
> disk implemented.  This reduces the risk of failure of the entire RAID
> if a single disk fails.  The RAID will simply function as if it were a
> RAID 5 until the failed disk is physically replaced and the RAID 6 or
> RAID ADG is rebuilt.
>
> As an alternative, if you have a controller that does not have RAID 6 or
> RAID ADG, then you can use RAID 5 with a spare disk set aside for use as
> a spareset in case of a failure.  This does not eliminate the risk in
> case of a single disk failure but it reduces it to the time required to
> rebuild the RAID using the spareset as opposed to the time it takes to
> physically replace a drive in a degraded RAID 5. If you suffer a second
> disk drive failure during the time that the RAID 5 is rebuilding after
> the first disk drive failure, then you will loose your entire RAID.
>
> The ultimate high availability configuration would be RAID 60+.  This
> would be two RAID 6 with their own sparesets assigned, mirrored to each
> other.  However, be prepared to loose a larger percentage of your raw
> disk drive space.  You will loose the equivalent of:
>
> Two disk drives for each RAID 6 used
> Two disk drives for each RAID 6 for redundant sparesets
> One raid 6 with the mirroring
>
> I really don't expect that you would build something like that for a
> home server but I figured I would throw all that out there just in case
> you had more money that you know what to do with and want to make sure
> the data on your server is safe from failure.
>
> Phil
>
> > -----Original Message-----
> > From: kclug-bounces at kclug.org
> > [mailto:kclug-bounces at kclug.org] On Behalf Of Luke-Jr
> > Sent: Tuesday, June 05, 2007 9:20 AM
> > To: kclug at kclug.org
> > Subject: Re: SATA PT2
> >
> > On Tuesday 05 June 2007 09:11, Phil Thayer wrote:
> > > Not to mention that with the recent SATA drive sizes to get
> > 1TB of SATA
> > > would only take 2 drive.  However, if you want to use a
> > multi-channel
> > > SATA controller with raid you will want to use smaller
> > drives (like 4 x
> > > 300 or 8 X 250) so you don't loose too much capacity to parity.
> >
> > With 8 drives, I'd probably want to make 2 parity for a
> > server... As unlikely
> > as it is for 2 drives to fail at once, that chance does
> > increase with # of
> > drives.
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