Actually it's better to just do mirrors. Avoid RAIDZ at all costs if you care about performance and the ability to resilver in a reasonable amount of time.
Are you referring to mirroring a volume or dataset on a single disk? Why would you want to do that instead of mirroring among multiple drives?
two sets of say 5 disks in a mirror raidz1 would still fail if a disk in one set failed and a disk in the other set failed. I guess you could do a stripe setup of 5 sets of 2 disks in mirrors. Still it seems wicked risky to me. I do agree though mirroring has been the best for speed but a lot of that changes with nicer SSDs especially NVMe ones.
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-...)
- [You should use mirror vdevs, not RAIDZ. : DataHoarder](https://www.reddit.com/r/DataHoarder/comments/2v0quc/you_sho...)