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