Encryption is the solution. A combination of at rest and on the fly encryption. They could still pull keys from ram, and they can also monitor your system over time. This all depends on your threat model. If you just want to upload your media collection and run a plex server. Just encrypt things. If you are running a drug market place… the fact that you asked this question… not only the fact that you had to ask it, but the very fact you asked it… well give up that dream. You will be caught very quickly.

I got 7 years out of my old zpool using them. The second I got a failure I got a load of new drives. I still have 3 drives out of that array I use in a raidz2 tripple that I keep as a cold backup. They are not showing a single issue, 9 years later at this point. I did have two failures though. The original array was 5 drives, and I purchased them in a couple staggered sets. The two that failed were the same later released sub-model that was different from the others, and purchased together, so probably the same bach.

I have never seen a drive without any issues reported by SMART. Not even brand new ones. Problems reported by SMART are more of a threshhold of amount of reported issues.

I would get brand and model matched ones and put them in a zpool with RAIDz2. You might opt for RAIDz1. Mixing drives is possible. But you will want to make sure the physical sector size and cache exactly match, and read/write speeds are close to matching (within 25-30 MB/s). For this and confirming the SMART readout crystaldiskinfo and crystaldiskmark are your friends… or smartctl and dd on linux.

I would say that $20 a piece are worth in it in the Aus market, but you should expect them to fail, and they are a temporary stopgap at that age. You should use them as a holdover while you save for a legitimate replacement.

It’s worth noting thate sas drives are not the same as sata. They a generally longer lived, they also tend to have a higher RPM, and thus a higher read/write rate. For this reason when you do replace them and move to a slower modern solution you should still use them for high speed access tasks. Like running VMs or databases. This only applies if they are 15k RPM ones, and for extra speed I would short strike them. You also should note that the sas connector is different from the sata connector. You will need a HBA or mobo with said ports and the associated sas cables.

In that formfactor. I would look into the NAS pi-Hats. There are a couple that take 4-5 2.5" drives. You could go for a tiny efficient builld.