4 ms·

So you setup two raid-z then stripe them for increased performance?

• unethical_ban 5y ago
  This is how I understand it. The hierarchy is disk < vdev < zpool. Disk is physical. vdev is logical. Purpose: Disk grouping and redundancy. Composition: One or more disks. zpool is logical. Purpose: Higher-level management of one or more vdevs. Composition: It acts like a JBOD. --- zpools can be thought of as "stripes of vdevs". This, in the narrow sense that the failure of any vdev in a zpool is a permanent loss of the entire zpool. All your redundancy in the ZFS ecosystem is via mirrored or RAID'ed vdevs. --- The setup I have heard of that balances performance, redundancy and space is to do what you say: Have a zpool of multiple mirror-type vdevs. You can also stripe at the vdev level, which I would assume has higher performance than having multiple single-disk vdevs in a pool - I'm unaware of the differences at a low level.
• oakwhiz 5y ago
  That's a common configuration for larger arrays where you probably don't want to make individual RAIDZ arrays too wide on their own. It's functionally similar to RAID 50 or 60. However when the budget is tight you might be incentivized to compromise on performance or reliability, so this new expansion feature really does help in hobbyist or shoestring budget situations where you just want one huge array to maximize usable space while still being able to tolerate some failures. Typically you would buy disks as you go along to try to stretch the budget further as utilization increases.