40TB x2. (Redundant backup.) Eventually going to pull all the drives and upgrade to 80TB x2.

I can answer that precisely!

...and I choose not to.

(But for real, I can answer it. 39.8TB isn't porn. The rest is gweempose in various states of undress.)

Just a quick reminder to people to MAKE SURE YOU HAVE A(n independent) BACKUP! A single computer running any type of RAID setup IS NOT a backup, you need something else in a separate case, preferably located someplace else. (External drives, second server, cloud backup, choose your poison.) Here's my tale of woe / don't be like Korn...

I have a 12 drive RAIDZ2 setup as my main storage library. Thousand-mile-up view is it's a setup where I can lose *any* of the twelve drives and not lose any data. Once drive three goes, however, you lose the whole thing. The idea is that if one drive dies, you go to the store right quick and buy a replacement and you're covered during the rebuild in case another drive dies.

Which is great in theory, except in my case I had two drives "die" simultaneously. A Y power splitter spontaneously decided it didn't want to continue living anymore, and off-lined two of my drives simultaneously. Now in my case it didn't cause any actual data loss since I'm running Z2 and can tolerate two drives going bad/offline. But if any of my other drives had a problem the whole thing would have been gone Gone GONE. Anyone with a typical RAID-5 setup would have been toast from the moment that Y-splitter let go.

The point is *things happen*, and the gold standard against loss is to make sure you have a good backup! In my case I have a completely redundant server/library that I automatically replicate everything to every three days, so even if a third drive died I'd have been out at most two days worth of data. As it was I replaced the power Y, brought the array back up, and since neither drive had physically failed it rewrote the missing data to both drives. It's now back to full resiliency (i.e. two drives can die and I'm OK). But I *easily* could have needed to use my backup had things not gone so well!

... Nor fast!