[EMAIL PROTECTED] wrote on 02/13/2007 09:48:54 AM:
> In the ZFS Best Practises Guide here:
>
>
http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide
>
> It says:
>
> ``Currently, pool performance can degrade when a pool is very full
> and file systems are updated frequently, such as on a busy mail
> server. Under these circumstances, keep pool space under 80%
> utilization to maintain pool performance.''
>
> What's the technical reason for this? Is there a CR describing this?
>
> I tried searching the archive, but didn't turn up anything obvious...
I don't know of any publicly available tech docs for this recommendation --
nor do I know that 80% is the "magic" number. I assume 80% is a safe
percentage to allow for COW/FS/slab overhead on busy filesystems with many
different workloads found in the wild. This type of recommendation exists
for many filesystems out there, usually 10% -> 20% to allow for best FS
behavior. For instance on VXFS, running into low space mode can slow
writes [b]incredibly[b] as free extents and other restructuring become very
high cost. As with any recommendation, you may find that on your systems
workload you can get way closer to "full" with no penalties.
-Wade
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