Importance of staying under 80% usage

[djdwosk97]

I have a two part question, so first off, how important is it to say below 80% capacity of a drive? And then what about 90%? What happens if you go over either of these limits? I've been running one of my drives at around 85-90% for over a month now because I'm not really sure of a good way to divide of the data, nor do I have another good place to put the data that I divide up (obviously at some point I'll have to buy a new drive).

And secondly, I've done a cursory search and the warning appears to be there to prevent you from accidentally filling your drive to 100% with snapshots of the system. I have snapshots disabled (should I enable them?), so is the capacity limit an issue -- assuming I'm conscious of what I upload and make sure I stay below 95% so the system doesn't lock up?

 

[depasseg]

The closer to full the pool gets, the more impact fragmentation will impact the performance. The 80% is a general guideline, but performance could be impacted starting under 50%. It depends on your usage.

As for filling. Don't let that happen. And it's not just snapshot related. If your pool fills up, bad things happen. My suggestion is to create a dataset called RESERVED, and reserve 50GB. This way if your pool gets completely full, you can reduce the reservation size to free up enough space to enable the deletion of files. If it's completely full, you could get into the situation that it's not possible to delete files.

 

[djdwosk97]

The closer to full the pool gets, the more impact fragmentation will impact the performance. The 80% is a general guideline, but performance could be impacted starting under 50%. It depends on your usage.

As for filling. Don't let that happen. And it's not just snapshot related. If your pool fills up, bad things happen. My suggestion is to create a dataset called RESERVED, and reserve 50GB. This way if your pool gets completely full, you can reduce the reservation size to free up enough space to enable the deletion of files. If it's completely full, you could get into the situation that it's not possible to delete files.

The drive is mainly for media storage, so nothing super critical.

Can the drive fill up on its own -- i don't know if there's some weird ZFS behavior (if snapshots are disabled)? Or can it only fill up if I add something to the drive?

And what would be the benefits of enabling snapshots (in a fully JBOD setup like mine).

 

[depasseg]

Can the drive fill up on its own -- i don't know if there's some weird ZFS behavior (if snapshots are disabled)? Or can it only fill up if I add something to the drive?

No the drive can't fill up on it's own. If you have snapshots then you should be aware that whatever data is captured in that snapshot will stay (that's the point of a snapshot - you can roll back time) until the snapshot is removed.

And what would be the benefits of enabling snapshots (in a fully JBOD setup like mine).

You should do more reading. What do you mean by JBOD?
A snapshot is a point in time. Whatever you do to the filesystem after taking a snapshot is tracked separately by the filesystem. so if you delete a file after taking a snapshot, the file will be gone but the space won't be freed up until the snapshot expires, or you delete it manually.

 

[Paul D Mallett]

Hi, I was about to ask about this so I have jumped in. Would it be good practice to place a "reservation" on the primary DataSet of around 80% to achieve the same effect as you describe above with a RESERVED data set with reserved space?