Hi Intel X-25 M are MLC not SLC, there are very good for L2ARC.
and next, you need more RAM: ZFS can't handle 4x 80 Gb of L2ARC with only 4Gb of RAM because ZFS use memory to allocate and manage L2ARC. 2010/2/10 Felix Buenemann <felix.buenem...@googlemail.com>: > Am 09.02.10 09:58, schrieb Felix Buenemann: >> >> Am 09.02.10 02:30, schrieb Bob Friesenhahn: >>> >>> On Tue, 9 Feb 2010, Felix Buenemann wrote: >>>> >>>> Well to make things short: Using JBOD + ZFS Striped Mirrors vs. >>>> controller's RAID10, dropped the max. sequential read I/O from over >>>> 400 MByte/s to below 300 MByte/s. However random I/O and sequential >>>> writes seemed to perform >>> >>> Much of the difference is likely that your controller implements true >>> RAID10 wereas ZFS "striped" mirrors are actually load-shared mirrors. >>> Since zfs does not use true striping across vdevs, it relies on >>> sequential prefetch requests to get the sequential read rate up. >>> Sometimes zfs's prefetch is not aggressive enough. >>> >>> I have observed that there may still be considerably more read >>> performance available (to another program/thread) even while a benchmark >>> program is reading sequentially as fast as it can. >>> >>> Try running two copies of your benchmark program at once and see what >>> happens. >> >> Yes, JBOD + ZFS load-balanced mirrors does seem to work better under >> heavy load. I tried rebooting a Windows VM from NFS, which took about 43 >> sec with hot cache in both cases. But when doing this during a bonnie++ >> benchmark run, the ZFS mirrors would win big time, taking just 2:47sec >> instead of over 4min to reboot the VM. >> So I think in a real world scenario, the ZFS mirrors will win. >> >> On a sitenote however I noticed that small sequential I/O (copying a >> 150MB sourcetree to NFS), the ZFS mirrors where 50% slower than the >> controllers RAID10. > > I had a hunch that the controllers volume read ahead would interfere with > the ZFS load-shared mirrors and voilà: sequential reads jumped from 270 > MByte/s to 420 MByte/s, which checks out nicely, because writes are about > 200 MByte/s. > >> >>> Bob >> >> - Felix > > - Felix > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
