[CentOS] ZFS on Linux in production?

Mon Nov 4 19:01:10 UTC 2013
John R Pierce <pierce at hogranch.com>

On 11/4/2013 10:43 AM, Les Mikesell wrote:
> On Mon, Nov 4, 2013 at 12:15 PM, Markus Falb
>> <wnefal at gmail.com>  wrote:
>>> >>
>> 3) NEVER let a zpool fill up above about 70% full, or the performance
>> >>really goes downhill.
>> >Why is it? It sounds cost intensive, if not ridiculous.
>> >Disk space not to used, forbidden land...
>> >Is the remaining 30% used by some ZFS internals?
> Probably just simple physics.  If ZFS is smart enough to allocate
> space 'near' other parts of the related files/directories/inodes it
> will have to do worse when there aren't any good choices and it has to
> fragment things into the only remaining spaces and make the disk heads
> seek all over the place.   Might not be a big problem on SSD's though.

even on 0 seek time SSDs, fragmenting files means more extents to track 
and process in order to read that file.

john r pierce                                      37N 122W
somewhere on the middle of the left coast