> > Given your question are you about to come back with a > case where you are not > seeing this? >
As a follow-up, I tested this on UFS and ZFS. UFS does very poorly: the I/O rate drops off quickly when you add processes while reading the same blocks from the same file at the same time. I don't know why this is, and it would be helpful if someone explained it to me. ZFS did a lot better. There did not appear to be any drop-off after the first process. There was a drop in I/O rate as I kept adding processes, but in that case the CPU was at 100%. I haven't had a chance to test this on a bigger box, but I suspect ZFS is able to keep the sequential read going at full speed (at least if the blocks happen to be written sequentially). I did these tests with each process being a "dd if=bigfile of=/dev/null" started at the same time, and I measured I/O rate with "zpool iostat mypool 2" and "iostat -Md 2". This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
