I just got done swapping all my drives out. I had 6x8tb drives in raidz2. About 8 months ago I had some sort of read errors on one drive with about 33k hours on it. I started swapping my drives out with 20tb drives one at a time, and just finished last week. So now I have 6x20tb drives with between 200 and 6k hours on them. The most hours on any of my older drives was about 40k, but other than a couple minor errors on the one drive, I’d had no issues with any of them. I’ve held onto all of the old drives, and was planning on setting up a second nas with 4x8tb drives in raidz1 to use as a backup server.
This was my second time replacing all my drives. My NAS is a bit like the ship of Theseus at this point, as it’s gone through many upgrades over the years. Started out with 6x3tb drives, and after about 4 years swapped the drives with 8tb units. About 5 years later (where we are now) it’s now 20tb drives. I’ve also swapped the chassis, mobo, CPU, and everything else out multiple times, etc.
My original setup was a mixture of desktop and Nas drives, but I’ve since been running all Nas/Enterprise drives. Based on my personal experience, it seems like I’ll replace drives every 4-5 years, regardless of actual failures… Both times I started the drive swaps there were read/write errors or sector failures on a drive in the pool. However, at around the same time I needed more space, so it was a convenient enough excuse to upgrade drive size.
As far as your concern about cramming drives into the chassis, always worth considering swapping chassis’s, but that’s up to you. I think 6 drives in Z2 is pretty happy compromise for number of drives and reliability. Thankfully your storage capacity is low enough you can pretty easily transfer everything off of that Nas to some interim storage location while you make whatever changes you want to.
Part of the reason I want to repurpose my old drives into another server is so I can have enough backup storage for critical files, etc should I need to start over with my main Nas.
I just went all refurbished on my new drives. Time will tell. Oldest one has about 8 months runtime on it.
I went with 5x recertified Seagate exos 20tb, and one recertified ironwolf pro 20tb.