Oh, I see. I thought you meant I should buy an 18 TB drive, move my data there, blow up my pool, create a RAIDZ2 pool, then move my data back. Yes, I agree I c

Oh, I see. I thought you meant I should buy an 18 TB drive, move my data there, blow up my pool, create a RAIDZ2 pool, then move my data back. Yes, I agree I could have reduced the risk of pool failure if I bought an extra 8 TB disk and not degraded the pool. So, it came down to do I for sure spend an extra $120 on an extra drive or do I just take the <1% chance that one of my three other disks fails in a 6-hour window while I'm migrating data. I took the chance, but I also had my data backed up in cloud storage at the file level in case there was a pool failure. In other words, it wasn't worth $120 to me to avoid a <1% risk that I'd have 8ish hours of hassle of recovering from cloud backup after a pool failure.