We (rsync.net) have several PB of raidz3 deployed all over the world.
We use conservatively sized (12-15 drive) vdevs and typically join 3 or 4 of those together to make a pool.
I can see getting nervous about raidz2 (sort of analogous to "raid6") after a drive failure ... but losing 4 drives out of 12 in a single raidz3 failure cascade is extremely improbable.
We all sleep quite well with this arrangement and have since we first migrated from UFS2 to ZFS in 2012.
We use conservatively sized (12-15 drive) vdevs and typically join 3 or 4 of those together to make a pool.
I can see getting nervous about raidz2 (sort of analogous to "raid6") after a drive failure ... but losing 4 drives out of 12 in a single raidz3 failure cascade is extremely improbable.
We all sleep quite well with this arrangement and have since we first migrated from UFS2 to ZFS in 2012.