True. I missed that on the RAID 0 as opposed to RAID 1.
Also, you would probable be surprised at the number of places that use the RAID 6 or RAID ADG in a mirrored configuration. It is not a fast or speedy solution. Remember that RAID 6 or RAID ADG is the SLOWEST RAID as far as performance is concerned. With RAID 10 you still open yourself up to vulnerability when a drive fails on your stripeset which causes your stripeset to fail. Since it is mirrored you are fine unless you have a failure on your mirrored stripeset. Personally, I don't like to use RAID 0 at anytime because it has no resiliency when it comes to disk failures. I would rather have the RAID 5 at a minimum for any single disk LUN and then use RAID 1 for additional redundancy. But generally I work with companies that are willing to spend the money for that configuration along with having controllers with the maximum read/write cache to compensate for the speed.
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From: Jeremy Fowler [mailto:jeremy.f76@gmail.com] Sent: Tuesday, June 05, 2007 2:17 PM To: Phil Thayer Cc: kclug@kclug.org Subject: Re: SATA PT2 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@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@kclug.org > [mailto: kclug-bounces@kclug.org mailto:kclug-bounces@kclug.org ] On Behalf Of Luke-Jr > Sent: Tuesday, June 05, 2007 9:20 AM > To: kclug@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. > _______________________________________________ > Kclug mailing list > Kclug@kclug.org > http://kclug.org/mailman/listinfo/kclug > _______________________________________________ Kclug mailing list Kclug@kclug.org http://kclug.org/mailman/listinfo/kclug