> In a case where a new vdev is added to an almost full zpool, more of > the writes should land on the empty device though, right? So maybe 2 > slabs will land on the new vdev for every one that goes to an > previously existing vdev.
(Un)Available disk space influences vdev selection. New writes will very likely end up on the empty vdev. > One problem that I'm having trouble getting my head around, and I'm > sure other are too, is that in terms of block allocation, zfs's > dynamic striping is absolutely nothing like raid-0. Correct me if I'm > wrong, but while the end result is similar (i/o is distributed against > all vdevs in the pool) the details are very different. That it's > compared to raid-0 just makes matters worse due to terminology overlap > and a preconception of how striping works. Dynamic striping doesn't > really seem to be striping at all - It's dynamically distributed block > allocation across the members of a zdev. The only thing that's nothing like RAID-0 is the device selection process for where a stripe/block goes. RAID-0 is dumb modulo, whereas ZFS makes educated guesses based on vdev stats. Since a file in ZFS is still being spread in fixed length pieces (default ZFS record size is 128KB, larger than what you usually find as stripe size in RAID-0s), I think calling it striping is still valid. Regards, -mg _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
