this post was submitted on 14 Jul 2025
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What's scrubbing for?
A ZFS Scrub validates all the data in a pool and corrects any errors.
I'm not in the know of having your own personal data centers so I have no idea. ... But how often is this necessary? Does accessing your own data on your hard drive require a scrub? I just have a 2tb on my home pc. Is the equivalent of a scrub like a disk clean up?
You usually scrub you pool about once a month, but there are no hard rules on that. The main problem with scrubbing is, that it puts a heavy load on the pool, slowing it down.
Accessing the data does not need a scrub, it is only a routine maintenance task. A scrub is not like a disk cleanup. With a disk cleanup you remove unneeded files and caches, maybe de-fragment as well. A scrub on the other hand validates that the data you stored on the pool is still the same as before. This is primarily to protect from things like bit rot.
There are many ways a drive can degrade. Sectors can become unreadable, random bits can flip, a write can be interrupted by a power outage, etc. Normal file systems like NTFS or ext4 can only handle this in limited ways. Mostly by deleting the corrupted data.
ZFS on the other hand is built using redundant storage. Storing the data spread over multiple drives in a special way allowing it to recover most corruption and even survive the complete failure of a disk. This comes at the cost of losing some capacity however.
Thank you for all this information. One day when my ADHD forces me into a making myself a home server I'll remember this and keep it in mind. I've always wanted to store movies but these days just family pictures and stuff. Definitely don't have terabytes but I'm getting up 100s of gb.