On Oct 3, 2009, at 10:26 AM, Chris Banal wrote:
On Fri, Oct 2, 2009 at 10:57 PM, Richard Elling <richard.ell...@gmail.com
> wrote:
c is the current size the ARC. c will change dynamically, as memory
pressure
and demand change.
How is the relative greediness of c determined? Is there a way to
make it more greedy on systems with lots of free memory?
AFAIK, there is no throttle on the ARC, so c will increase as the I/O
demand
dictates. The L2ARC has a fill throttle because those IOPS can compete
with the other devices on the system.
> 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
You want to cache stuff closer to where it is being used. Expect the
L2ARC
to contain ARC evictions.
If c is much smaller than zfs_arc_max and there is no memory
pressure can we reasonably expect that the L2ARC is not likely to be
used often? Do items get evicted from the L2ARC before the L2ARC is
full?
Yes, but I'm not exactly sure when this arrived. Rather than repeat,
the description
is fairly well documented in the source (note: line number subject to
change, look
for the comments describing the L2ARC).
http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c#3638
-- richard
_______________________________________________
zfs-discuss mailing list
zfs-discuss@opensolaris.org
http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
