On Mon, May 4, 2009 at 10:12 AM, Mark Saad <ms...@datapipe.com> wrote: > > Hello List > Worked on breaking ZFS we came across a interesting question; > What is the lowest tested ZFS ARC Cache size ?
I haven't tested it with just over 64MB, but the code indicates that that is the lowest you should try. http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c 3500 /* 3501 * Allow the tunables to override our calculations if they are 3502 * reasonable (ie. over 64MB) 3503 */ 3504 if (zfs_arc_max > 64<<20 && zfs_arc_max < physmem * PAGESIZE) 3505 arc_c_max = zfs_arc_max; 3506 if (zfs_arc_min > 64<<20 && zfs_arc_min <= arc_c_max) 3507 arc_c_min = zfs_arc_min; >Also could you reliably > run with it set to 0 ? For better and worse, ZFS isn't primarily a file system. It is a transactional object store that has a file system as one type of object. The ARC is not a file system buffer cache, it caches virtual device blocks. You might think of it as being more like a very large write-back drive cache. It might work with less than 64MB, but the ARC buffers are what ZIO sends down to disk so it certainly would not work with zero. Cheers, Kip _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
