In a discussion a few weeks back, it was mentioned that the Best Practices Guide says something like "Don't put more than ___ disks into a single vdev." At first, I challenged this idea, because I see no reason why a 21-disk raidz3 would be bad. It seems like a good thing.
I was operating on assumption that resilver time was limited by sustainable throughput of disks, which was wrong. At present, resilver time is limited by random IO, so the ZFS resilver time is typically much longer than it would be if you were resilvering the whole disk serially. But that was the only negative against 21-disk raidz3. That was the only negative, against using more than ___ disks in a single vdev. Assuming this one problem is improved at some point, is there any other reason to stay below ___ disks in a vdev? Does the random IO resilver performance problem also apply to scrub or zfs send? Again the problem is: resilver is done in effectively random order, so the disks perform zillions of random seeks instead of serializing IO and minimizing seeks during resilver. Is the same thing true for scrub or zfs send? _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
