On 11/04/2013 08:01 PM, John R Pierce wrote:
On 11/4/2013 10:43 AM, Les Mikesell wrote:
On Mon, Nov 4, 2013 at 12:15 PM, Markus Falb
wnefal@gmail.com wrote:
- 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.
but why would this be much worse with ZFS than eg ext4?