On July 14, 2008 7:49:58 PM -0500 Bob Friesenhahn <[EMAIL PROTECTED]> wrote: > This seems like a bunch of hog-wash to me. Any time you see even a > single statement which is incorrect, it is best to ignore that forum > poster entirely and if no one corrects him, then ignore the entire forum.
I don't know what "forums" you're on, but in my experience that would eliminate approximately 100% of them. > For example, from what I have read, RAID-Z does not always write a full > stripe. While RAID-Z uses parity similar to RAID-5 and writes a stripe > across disks, it does not need to write across all the disks like RAID-5 > does. If you had 10 disks, it might decide to stripe across 6 disks per > block write. Which is a "full stripe" in that the parity calculation covers the entire write. >> It sounds like they're talking more about traditional hardware RAID >> but is this also true for ZFS? Right now I've got four 750GB drives >> that I'm planning to use in a raid-z 3+1 array. Will I get markedly >> better performance with 5 drives (2^2+1) or 6 drives 2*(2^1+1) >> because the parity calculations are more efficient across N^2 >> drives? > > With ZFS and modern CPUs, the parity calculation is surely in the noise > to the point of being unmeasurable. I would agree with that. The parity calculation has *never* been a factor in and of itself. The problem is having to read the rest of the stripe and then having to wait for a disk revolution before writing. -frank _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
