[ssl-3]

The cost of a scrub is just a flurry of disk reads and a reduction in performance during a scrub.

If this cost is affordable on a daily basis, then do a scrub daily. If it's only affordable less often, then do it less often.

(Whatever the case: It's not like a scrub causes any harm to the hardware or the data. It can run as frequently as you elect to tolerate.)

[agapon]

With HDDs, it's also mechanical wear and increased chance of a failure. SSDs are not fully immune to increased load either.

[ssl-3]

Is there any evidence that suggests that reading from a hard drive (instead of it just spinning idle) increases physical wear in any meaningful way? Likewise, is there any evidence of this for solid-state storage?

[rcxdude]

Yes. Hard drives have published "Annualized Workload Rate" ratings, which are in TB/year, and the manufacturers state there is no difference between reads and writes for the purpose of this rating.

(https://www.toshiba-storage.com/trends-technology/mttf-what-...)

For SSDs, writes matter a lot more. Reads may increase the temperature of the drive, so they'll have some effect, but I don't think I've seen a read endurance rating for an SSD.

[digiown]

Reading from it requires the read head to move, as opposed to spinning idle where the heads are parked on the side. Moving parts generally wear out over time.