Jonathan Wheeler wrote: I'm not a ZFS expert - I'm just an enthusiastic user inside Sun.
Here are some brief observations: > Bonnie > -------Sequential Output-------- ---Sequential Input-- > --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- > --Seeks--- > raid0 MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU > 8 disk 8196 78636 93.0 261804 64.2 125585 25.6 72160 95.3 246172 19.1 286.0 > 2.0 > 8 disk 8196 79452 93.9 286292 70.2 129163 26.0 72422 95.5 243628 18.9 302.9 > 2.1 > > so ~270MB/sec writes - awesome! 240MB/sec reads though - why would this be > LOWER then writes?? I believe this can happen because ZFS is optimized for writes, though I would tend expect a sequential write followed by a sequential read to be about the same if there's no other filesystem activity during the write. > -------Sequential Output-------- ---Sequential Input-- > --Random-- > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- > --Seeks--- > mirror MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU > 8 disk 8196 33285 38.6 46033 9.9 33077 6.8 67934 90.4 93445 7.7 230.5 > 1.3 > 8 disk 8196 34821 41.4 46136 9.0 32445 6.6 67120 89.1 94403 6.9 210.4 > 1.8 > > 46MB/sec writes, each disk individually can do better, but I guess keeping 8 > disks in sync is hurting performance. The 94MB/sec writes is interesting. One > the one hand, that's greater then 1 disk's worth, so I'm getting striping > performance out of a mirror GO ZFS. On the other, if I can get striping > performance from mirrored reads, why is it only 94MB/sec? Seemingly it's not > cpu bound. I expect a mirror to perform about the same as a single disk for writes, and about the same as two disks for reads, which seems to be the case here. Someone from the ZFS team can correct me, but I tend to believe that reads from a mirror are scheduled in pairs; it doesn't help the read performance to have 6 more copies of the same data available. > Now for the important test, raid-z I'll have to let the experts dissect this data; it looks a little goofy to me, too. Dana _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
