Yellow alert, 80% threshold

[diskdiddler]

I've hit 80% threshold on my system and got an alert.
I know it's logical to leave some breathing room - but how bad is it going to say 95%? It's a 6x5TB array, 18TB total free space?

I would assume the space I 'lost' for redundancy should be all the system needs, besides maybe 2 or 3% for potential re-allocated clusters or something?

Any comments on this?

 

[gpsguy]

Don't even think of going to 95%. 100% is just around the corner and when you hit that, you'll be in a world of hurt, especially if you have snapshots. Deleting files to free up space is nearly impossible. Search the forum for "disk full" threads to see what happens.

Depending on the services used, you'll start to see performance tank as you fill the volume.

 

[diskdiddler]

Well 5% of 18TB is still 900gb of space I can leave clear - I'm fine with that personally. I don't take snapshots - but I do see your point about it potentially being quite nasty.
I mean I take it - NEVER fill the disk and leave a buffer but 20% seems kinda high, no?
What if my array was 580TB am I to leave 11TB unused?

 

[gpsguy]

Here is a thread from yesterday/today on the same topic. See: https://forums.freenas.org/index.php?threads/dont-go-over-80.25068/#post-156408

 

[pschatz100]

Well 5% of 18TB is still 900gb of space I can leave clear - I'm fine with that personally. I don't take snapshots - but I do see your point about it potentially being quite nasty.
I mean I take it - NEVER fill the disk and leave a buffer but 20% seems kinda high, no?
What if my array was 580TB am I to leave 11TB unused?

The short answer to your question is "yes." If you read up on ZFS, the documentation says that performance falls dramatically after you hit 80% of your capacity. The gurus here on the forum can explain why. Since I am not familiar with the intricacies of ZFS, I just make it a point to follow best practice as much as possible.

If your system gets too full, you will experience performance and stability problems. I did this once, and I can guarantee that I will not let it happen again. Disk is cheap compared to the value of my data and time.

 

[Ericloewe]

The short answer to your question is "yes." If you read up on ZFS, the documentation says that performance falls dramatically after you hit 80% of your capacity. The gurus here on the forum can explain why. Since I am not familiar with the intricacies of ZFS, I just make it a point to follow best practice as much as possible.

If your system gets too full, you will experience performance and stability problems. I did this once, and I can guarantee that I will not let it happen again. Disk is cheap compared to the value of my data and time.

I'll add that if the pool fills up completely, you're in for a world of pain.