On Mar 27, 2010, at 2:41 AM, Daniel Carosone wrote: > On Sat, Mar 27, 2010 at 01:03:39AM -0700, Erik Trimble wrote: > >> You can't share a device (either as ZIL or L2ARC) between multiple pools. > > Discussion here some weeks ago reached suggested that an L2ARC device > was used for all ARC evictions, regardless of the pool. > > I'd very much like an authoritative statement (and corresponding > documentation updates) if this was correct.
I'm responsible for propagating this false rumor. It is the result of some testing in which my analysis was flawed. The authoritative response is, as usual, in the source. l2arc_write_eligible() checks the spa (read: zpool) to see if the buffer belongs to it. If not, the buffer is not sent to the l2arc. See the source on or near http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/arc.c#3729 I still think this is a useful thing and believe it can be implemented relatively easily. I'm thinking along the lines of having a property for the pool to share the cache. Besides handling the property itself, it looks like there are only a few (perhaps as few as 5) lines of code needed to change the eligibility and handle flushing. However, this idea may collide with the persistent l2arc project. -- richard-who-would-prefer-to-eat-his-eggs-rather-than-wear-them ZFS storage and performance consulting at http://www.RichardElling.com ZFS training on deduplication, NexentaStor, and NAS performance Las Vegas, April 29-30, 2010 http://nexenta-vegas.eventbrite.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
