> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of MLR
> Say we get a decent ssd, ~500MB/s read/write. If we have a 20 HDD
> setup shouldn't we be reading at least at the 500MB/s read/write range?
> would we want a ~500MB/s cache?
You don't add l2arc because you care about MB/sec. You add it because you
care about IOPS (read).
Similarly, you don't add dedicated log device for MB/sec. You add it for
IOPS (sync write).
Any pool - raidz, raidz2, mirror - will give you optimum *sequential*
throughput. All the performance enhancements are for random IO. Mirrors
outperform raidzN, but in either case, you get improvements by adding log &
> Am I correct in
> thinking this means, for example, I have a single 14 disk raidz2 vdev
It's not advisable to put more than ~8 disks in a single vdev, because it
really hurts during resilver time. Maybe a week or two to resilver like
> disks will go ~100MB/s each , this zpool would theoretically read/write at
No matter which configuration you choose, you can expect optimum throughput
from all drives in sequential operations. Random IO is a different story.
> What would be the best setup? I'm thinking one of the following:
> a. 1vdev of 8 1.5TB disks (raidz2). 1vdev of 12 3TB disks (raidz3)?
> (~200MB/s reading, best reliability)
No. 12 in a single vdev is too much.
> b. 1vdev of 8 1.5TB disks (raidz2). 3vdev of 4 3TB disks (raidz)?
> reading, evens out size across vdevs)
Not bad, but different size vdev's will perform differently (8 disks vs 4)
so... See below.
> c. 2vdev of 4 1.5TB disks (raidz). 3vdev of 4 3TB disks (raidz)?
> reading, maximize vdevs for performance)
This would be your optimal configuration.
zfs-discuss mailing list