I was curious about what a "nested" mirror is really. What exactly is nested? I'd setup a large pool with mirror vdevs, i.e. n sets of 2 disks per mirror. My

I was curious about what a "nested" mirror is really. What exactly is nested? I'd setup a large pool with mirror vdevs, i.e. n sets of 2 disks per mirror. My half-remembered reasoning was that backups manage the risk you'll lose data. But replacing a disk in a mirror vdev is much easier, and faster, than doing so with RAIDZ. The risk of RAIDZ is that resilvering impacts multiple vdevs, is much more intensive than a simple mirror resilvering, and thus the probability that additional drives will fail is much higher. Here's a blog post that I definitely read the last time I was reading up on this: - [ZFS: You should use mirror vdevs, not RAIDZ. – JRS Systems: the blog](http://jrs-s.net/2015/02/06/zfs-you-should-use-mirror-vdevs-not-raidz/ http://jrs-s.net/2015/02/06/zfs-you-should-use-mirror-vdevs-...)