> zfs will use as much memory as is "necessary" but how is "necessary" calculated?
using arc_summary.pl from http://www.cuddletech.com/blog/pivot/entry.php?id=979 my tiny system shows: Current Size: 4206 MB (arcsize) Target Size (Adaptive): 4207 MB (c) Min Size (Hard Limit): 894 MB (zfs_arc_min) Max Size (Hard Limit): 7158 MB (zfs_arc_max) so arcsize is close to the desired c, no pressure here but it would be nice to know how c is calculated as its much smaller than zfs_arc_max on a system like yours with nothing else on it. > When an L2ARC is attached does it get used if there is no memory pressure? My guess is no. for the same reason an L2ARC takes sooooo long to fill. arc_summary.pl from the same system is Most Recently Used Ghost: 0% 9367837 (mru_ghost) [ Return Customer Evicted, Now Back ] Most Frequently Used Ghost: 0% 11138758 (mfu_ghost) [ Frequent Customer Evicted, Now Back ] so with no ghosts, this system wouldn't benefit from an L2ARC even if added In review: (audit welcome) if arcsize = c and is much less than zfs_arc_max, there is no point in adding system ram in hopes of increase arc. if m?u_ghost is a small %, there is no point in adding an L2ARC. if you do add a L2ARC, one must have ram between c and zfs_arc_max for its pointers. Rob _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
