On Tue, 18 Aug 2009, Greg wrote:
Hello all, I have searched everywhere but sadly I have not yet found any information on how to do this. I have raid 2 perc 5i raid controllers in a server, what I would like to do is do a raid 10 setup, however the catch is I would like the controller to handle the striping and opensolaris to handle the mirroring, this way I can use the cache on the card and still get the benefits of zfs. I will be doing 4 different raid 10 pools. The only way I have found is making single disk raid 0 arrays on the card and letting solaris do what is needed. However I believe this to be raid 0+1 and not raid 10. Is this correct? Any posts or just simple pointers in the right direction would be great. Thanks!
From WikiPedia (http://en.wikipedia.org/wiki/RAID):
"RAID 1+0: mirrored sets in a striped set (minimum four disks; even number of disks) provides fault tolerance and improved performance but increases complexity. The key difference from RAID 0+1 is that RAID 1+0 creates a striped set from a series of mirrored drives. In a failed disk situation, RAID 1+0 performs better because all the remaining disks continue to be used. The array can sustain multiple drive losses so long as no mirror loses all its drives."
It is my understanding that this is close to what ZFS's load-sharing across mirror vdevs accomplishes with the difference that ZFS uses load-sharing (writes full block to a drive) rather than true striping (spliting blocks) across the mirrors. ZFS wastes fewer IOPS than true striping.
I am using a setup with SAN drives exported as "RAID 0" and ZFS managing the drives as mirror pairs. This works well as long as your controller is able to present reliable "RAID 0" LUNs and is able to sustain the 2X increased write load caused by mirroring in software. If you have two controllers then splitting the mirrors across the controllers should produce excellent performance and reliability.
Bob -- Bob Friesenhahn [email protected], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
