on Fri May 22 2009, Richard Elling <richard.elling-AT-gmail.com> wrote:
> David Abrahams wrote: >> http://groups.google.com/group/zfs-fuse/msg/5fac5eaf2c7fccb8 shows some >> (admittedly very crude) tests I did with OpenSolaris 0906, with some >> very surprising performance results. In particular, read speed on an >> 8-disk pool seemed to drop by 50% when I set up the pool to use RAIDZ2. >> >> Can anyone shed light on why that might be the case? >> > > You are likely disk I/O bound. Even if I were, that shouldn't account for such a dramatic difference AFAICT. Shouldn't this hold: raidz2 / flatzfs = (raidpoolsize - raidparitybits) / (flatpoolsize) ?? In my case raidpoolsize=flatpoolsize=8 and paritybits=2, so the ratio should be 0.75, not 0.5. Or am I missing something? > Look at the disk traffic to locate your bottleneck. How does one look at the disk traffic? > FWIW, if you enable compression, your benchmark will be > much faster :-) Of course, but writing a string of zeroes to a compressed filesystem only tests the compression speed, which is of little or no interest to me. Incidentally, I have some speed tests of a compressed zfs here: http://groups.google.com/group/zfs-fuse/browse_thread/thread/b55a25ea432b416 but as the message implies, it's hard to know whether those results mean anything. -- Dave Abrahams BoostPro Computing http://www.boostpro.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
