80% Rule

[jvioncek]

I've read lots about using only 80% of available space but I can't seem to find if the free space should be left when sizing the zvol or free space left in the file system.

 

[Johnny Fartpants]

The 80% rule is based on the size of your entire zpool. FreeNAS gives you a nice % value at the top of your pool so just don't exceed that.

 

[jvioncek]

So based on that I should be in the clear?

 

[Johnny Fartpants]

What are you doing with the zvol, iSCSI?

 

[jvioncek]

Yes

 

[Johnny Fartpants]

50% rule with zvol and iSCSI.

 

[jvioncek]

Right, I read that. You mentioned the percentage at the top of the pool, I see only 29% utilization. Based on that it sounds like it doesn't matter where the free space is located (zvol, pool, filesystem) as long as it exists somewhere?

 

[jgreco]

You can go far beyond 50% utilization on block storage, but the performance will tend to degrade into sucksville with time. Your best bet is to use around 10-25% space if you really want sustained high performance. At 50% the steady state performance is already pretty tragic. Feel free to search the forums for "steady state" and "jgreco" as I discuss this often.

 

[jvioncek]

Thanks for your help! I cleaned up the storage and got my space utilization down to about 30% and my writes are now maxing the 10GB link.

 

[jgreco]

For more info see the sticky "The path to success for block storage" at the top of this forum.