My boot USB suddenly failed (won't detect in any of my other 3 windows machines) and I stupidly didn't have a backup. I have created a new boot USB using the creation tool, and connecting to the machine I can see that all of my storage devices are showing and appear healthy (6x 16TB HDD). I also had 2x 500GB SSDs which were used in a cache pool, and some dockers configured like a jellyfin server, etc.

Could I please have some assistance getting my ZFS pool back before I accidentally destroy my data. From my understanding of RAIDZ2, the 2 drives worth of parity is striped across all devices, meaning that none of the devices in the vdev would be dedicated to parity. Does this mean that I can simply reassign all 6 devices to a new vdev in RAIDZ2, then add the cache drives to the pool after the fact? I'm looking for a step by step here honestly since I'm not 100% up to speed on ZFS terminology

If anyone feels inclined to offer advice once I've recovered my data and can set things up in a different way, please share away:

1. I felt that the RAIDZ2 offered my preferred balance of capacity and redundancy, and the SSD cache was thrown in since they're just laying around. Is there a better way to utilise these devices whilst still giving me decent redundancy?

2. What's the preferred method of backing up the boot USB for future failures? I seldom boot my unraid machine (hence my surprise at the failure) to run my media server or tinker with it, so backing it up every time it turns on doesn't seem like a bad idea. Is there a simple way to backup the flash to my main PC when the unraid machine boots?

Edited August 28, 2025Aug 28 by dotaman

You should be able to just reimport both pools, for ech pool do this:

on main, create a new pool with the same name and number of slots

assign the pool device(s), order doesn't matter (assuming Unraid 7.0+), leave the filesystem set to auto

repeat for other pools, then start the array to import the pool