thanks, bill. i killed an old filesystem. also forgot about arc_meta_limit. kicked it up to 4gb from 2gb. things are back to normal.
On Thu, Dec 15, 2011 at 1:06 PM, Bill Sommerfeld <sommerf...@alum.mit.edu> wrote: > On 12/15/11 09:35, milosz wrote: >> >> hi all, >> >> suddenly ran into a very odd issue with a 151a server used primarily >> for cifs... out of (seemingly) nowhere, writes are incredibly slow, >> often<10kb/s. this is what zpool iostat 1 looks like when i copy a >> big file: >> >> storepool 13.4T 1.07T 57 0 6.13M 0 >> storepool 13.4T 1.07T 216 91 740K 5.58M > > ... > >> any ideas? pretty stumped. > > > Behavior I've observed with multiple pools is that you will sometimes hit a > performance wall when the pool gets too full; the system spends lots of time > reading in metaslab metadata looking for a place to put newly-allocated > blocks. If you're in this mode, kernel profiling will show a lot of time > spent in metaslab-related code. > > Exactly where you hit the wall seems to depend on the history of what went > into the pool; I've seen the problem kick in with only 69%-70% usage in one > pool that was used primarily for solaris development. > > The workaround turned out to be simple: delete stuff you don't need to keep. > Once there was enough free space, write performance returned to normal. > > There are a few metaslab-related tunables that can be tweaked as well. > > - Bill _______________________________________________ zfs-discuss mailing list firstname.lastname@example.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss