> I don't recall why, but I've heard that RAIDZ should be avoided, in favor of stripped mirrors.
Most people care about random IO (also once your filesystem has been populated and in use for a while, true linear IO really ceases to be due to fragmentation.) Striped arrays lose random IO performance as drive count goes up; an array of mirrored pairs gains random IO performance. This is less of an issue with tiered storage and cache devices, especially given you almost have to work to find an SSD less than 256GB these days.
You can only upgrade a zdev by upgrading all its drives; it's a lot nicer cash-flow-wise to gradually upgrade a mirrored pair here and there, or upgrade exactly how many pairs you need to for the space you need.
With RAID-Z you have a drive fail and pray a second doesn't fail during the resilver. With RAID-Z2 you can have any two drives fail. With mirrors you can lose 50% of your drives (provided that they're the right drives.)
> You can only upgrade a zdev by upgrading all its drives
This is no longer the case, or at least, should no longer be the case soon. The ability to add drives to a zpool has been announced, and will trickle through to stable before too long.
Most people care about random IO (also once your filesystem has been populated and in use for a while, true linear IO really ceases to be due to fragmentation.) Striped arrays lose random IO performance as drive count goes up; an array of mirrored pairs gains random IO performance. This is less of an issue with tiered storage and cache devices, especially given you almost have to work to find an SSD less than 256GB these days.
You can only upgrade a zdev by upgrading all its drives; it's a lot nicer cash-flow-wise to gradually upgrade a mirrored pair here and there, or upgrade exactly how many pairs you need to for the space you need.
With RAID-Z you have a drive fail and pray a second doesn't fail during the resilver. With RAID-Z2 you can have any two drives fail. With mirrors you can lose 50% of your drives (provided that they're the right drives.)