NAS: Disk Upgrades
Almost 8 years ago now we scratched together enough to buy new disks for a shiny new ZFS pool. We were short on both hardware and cash, so we just went with a RAIDZ configuration of three 4TB disks. This gave us approximately 8TB of usable space, and the ability to lose any one of the disks without losing our data.
It’s performed admirably over the years, though we have, several times now, had to bucket out things to make space as it reached the dreaded 85% threshold (which isn’t really a thing any more, technically, but it’s a good spot to think “I’m running out of storage” for sure). Last year, it became clear that there wasn’t much track left in that approach, and I wanted some room to set up snapshots and a 3-2-1 backup regime and didn’t really have the space to start it.
But we weren’t about to drop a few thousand bucks on disks before Christmas, so it had to wait. Come February, I was going to do it, but we had a few vet visits that meant funds were a bit tight… so I basically decided I was going to put it off for another month. Then came the news: Western Digital have sold their capacity of hard drives for 2026 due to the incredibly infuriating AI bubble. Most folks around seemed to think this meant the prices would skyrocket, and they’d already gone up a good $20/drive at this rate, so I wasn’t about to sit around and wait to find out.
This did, unfortunately, mean that I bought all the drives in one order, from the same retailer. This is, according to superstition, less than optimal as they might be all from the same batch and if there’s a defect in the batch, you could lose the pool. I am not superstitious, but I am a little stitious, so this made me uneasy. However… if I waited, and then could not buy any disks (I’m not sure this would have happened, but bear with me) then I’d be running on 8 year old disks that were full anyway. Second, I need to take backups more seriously (the cobbler’s kids are definitely barefoot in this case, I spent so long lecturing my IT clients in the early 2000s about backups and I am straight-up dogshit at it), and if I have decent backups then losing the pool is just downtime rather than data loss. Third, I’m impatient as fuck and I wanted to just spend the cash and be done with it.
The disks arrived on Thursday. 8 of them, all 8TB WD Red Plusses. And yes, most of them are suspiciously close together in serial numbers. Ahh well, maybe the machine spirit will take pity on me.
Anyway, after quite a bit of fucking about (I went with 8 disks because it would fill the storage server’s hot-swap bays, not thinking about how I would put the other three disks in to copy the data across), we now have a RAIDZ2 pool of the 8 disks. This gives us about 48TB usable space, or 6x what we had. It also lets us lose any two disks from the pool without losing data. I thought about going with striped mirrors, but I don’t really need the performance and it’s nice to be able to lose any two disks, whereas with striped mirrors you can lose up to four disks, but only if they’re the right disks, if you lose the wrong two, data is gone.
So today, while I’m at it, I took everything down and did the final copy across, and then reinstalled Ubuntu on the machine… because it’s a continually-upgraded Xenial machine and there’s a lot of cruft on it, a clean slate is always nice. Got it up and running, and with a bit of grief and undoing all the NFS/iSCSI work I did (I’ll set those up again later, maybe, maybe I’ll just use Longhorn for everything not already on the disk box) and most things are up. As I write this, collectd and my Mozilla sync server aren’t up, I’ll probably do that tomorrow.
I did have one issue where one of the disks jumped out of the pool briefly, I am fairly sure that’s cable-related though… I swapped that disk around with another one and the other disk jumped out. So I unplugged and replugged the cables to that part of the backplane and so far so good, but I will definitely keep an eye on it.
I plan on finding a box to put the old disks in and using it as an on-site backup host, and then I’ll set up something like Wasabi or similar using Restic for off-site.
Here’s to - hopefully - 8 more years!
Update: 2026-03-08: Looking at them again, the disks I bought have already gone up a further $35/disk, meaning that for 8 disks I saved ~$280 by not waiting.
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