3

Does the 80% capacity rule of thumb for ZFS pools apply regardless of the size of the pool? If I have a pool of 10TB, that means I have to keep 2TB free. Fair enough, the loss isn't too great. But in a 50TB pool, that means I need to keep 10TB free. That's a lot of free space left over...

3

Yes. The 80% rule applies... (with some exceptions)

Think about it the same way you'd approach monitoring of a volume. 90% full is 90% regardless of the actual capacity and would still yield an alert.

This is no different. You don't want to plan or expect to run at that high of a capacity.

  • I don't know about you, but I don't care about a volume being X% full, so much as I care about, "is this going to fill up and cause me grief any time soon?" If I've got a 100TB volume, with a usage growth rate of, say, 10GB/day, and a week's lead time on provisioning new capacity, I'm not going to give a flying fig when it's got 10TB (or 20TB) free. I'll start to care when it's down to 1-2TB free. – womble Nov 6 '15 at 2:18
  • 3
    Except copy-on-write filesystem performance tends to degrade heavily above 85% usage. If snapshots are involved, it's VERY easy for an inadvertent action to exhaust filesystem space. This is why people strongly suggest remaining below 80% on ZFS filesystems. – ewwhite Nov 6 '15 at 2:21
  • Sure, but that's unrelated to an analogy of monitoring volume capacity. – womble Nov 6 '15 at 3:07
  • 2
    No it isn't unrelated - it's directly saying performance degrades above x% regardless of how long it would take to fill the remaining space, so there's a specific reason to care. You can still say "I don't care about that" but that implies you don't give a flying fig about storage performance... – TessellatingHeckler Nov 6 '15 at 3:17

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.