3 ms·

SMR on a z-mirror is quite a bit different than a raidz/2/3 setup due to how SMR works. A mirror will do much better at optimizing the writes for SMR rebuild.

SMR on a z-mirror is quite a bit different than a raidz/2/3 setup due to how SMR works. A mirror will do much better at optimizing the writes for SMR rebuild. When using raidz, your milage may vary, as they say. It absolutely will work. Before I knew the difference between SMR & CMR, and when WD obscured this on their reds, I bought SMR to use in a raid2 setup. I first noticed something was wrong when sequential write performance would begin to tank sharply on the drives and it wasn't due to the ZiL. Replacement of a failed drive was slow, very slow but I would work. After 5 years in service I replaced them with CMR drives one at a time. The replacement speed from the first to the last increase about 3x. So don't agree with the doom sayers about SMR but for the few $ more over the course of 5 years, I'll go with the speed.

vermaden 2y ago
Yes, it will 'hurt' more to use SMR drives with raidz1/raidz2/raidz3. ... but I believe ZFS DRAID mode will not hurt that much on SMR drives. In ZFS DRAID there is no dedicated SPARE drives - but 'spare blocks' are spread across the disks along with 'data blocks' and 'parity blocks' - this means that all drives 'read' for the resilver and all drives 'write' for the resilver. More here: - https://github.com/openzfs/zfs/wiki/dRAID-HOWTO/001b44728e1ac3329a4d91be97bcd565a8f351b7 https://github.com/openzfs/zfs/wiki/dRAID-HOWTO/001b44728e1a... ... also the Sequential Resilver helps even more: - https://docs.google.com/presentation/d/1vLsgQ1MaHlifw40C9R2sPsSiHiQpxglxMbK2SMthu0Q/edit#slide=id.g995720a6cf_1_19 https://docs.google.com/presentation/d/1vLsgQ1MaHlifw40C9R2s...