I don't think you'd see the same performance benefits on RAID-Z since parity isn't always on the same disk. Are you seeing hot/cool disks?
Adam On Sun, Nov 05, 2006 at 04:03:18PM +0100, Pawel Jakub Dawidek wrote: > In my opinion RAID-Z is closer to RAID-3 than to RAID-5. In RAID-3 you > do only full stripe writes/reads, which is also the case for RAID-Z. > > What I found while working on RAID-3 implementation for FreeBSD was that > for small RAID-3 arrays there is a way to speed up random reads up to > 40% by using parity component in a round-robin fashion. For example > (DiskP stands for partity component): > > Disk0 Disk1 Disk2 Disk3 DiskP > > And now when I get read request I do: > > Request number Components > 0 Disk0+Disk1+Disk2+Disk3 > 1 Disk1+Disk2+Disk3+(Disk1^Disk2^Disk3^DiskP) > 2 Disk2+Disk3+(Disk2^Disk3^DiskP^Disk0)+Disk0 > 3 Disk3+(Disk3^DiskP^Disk0+Disk1)+Disk0+Disk1 > etc. > > + - concatenation > ^ - XOR > > In other words for every read request different component is skipped. > > It was still a bit slower than RAID-5, though. And of course writes in > RAID-3 (and probably for RAID-Z) are much, much faster. > > -- > Pawel Jakub Dawidek http://www.wheel.pl > [EMAIL PROTECTED] http://www.FreeBSD.org > FreeBSD committer Am I Evil? Yes, I Am! > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss -- Adam Leventhal, Solaris Kernel Development http://blogs.sun.com/ahl _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
