> - When the filesystems have compress=ON I see the following: reads from compressed filesystems come in waves; zpool will report for long durations (60+ seconds) no read activity while the write activity is consistently reported at 20MB/S (no variation in the write rate throughtout the test).
My guess is that your benchmark is writing blocks of zeroes. With compression enabled, ZFS will not merely compress blocks of zeroes, it will eliminate them -- i.e. turn them into holes. The only thing left to write is znode updates (mtime, etc). This will appear as a very a low disk I/O rate because it is; to measure the logical I/O rate, I'd suggest just timing it. > BTW, we love the ZFS and are looking forward to rolling out aggresively in > our new project. I'd like to take advantage of the compression since we're mostly I/O bound and we've plenty of CPU/Memory. Great! Please let us know if this explains the mystery. Jeff _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
