ZFS L2ARC [PSARC/2007/618 FastTrack timeout 10/31/2007]

[James Carlson]

Matthew Ahrens writes:
> This case adds capability to ZFS to use storage devices as a level 2 ARC
> (L2ARC), caching read requests that would otherwise be satisfied by disk.
> Random read performance can then be improved by adding fast storage
> devices to the L2ARC, such as short-stroked disks, solid state disks,
> and other media with substantially faster read latency than disk.

Is there any way to determine whether a given cache device is helping
or hurting me?  Perhaps some statistics that can be viewed?

Any rule of thumb about choosing such a device?  How much faster than
main storage does it need to be in order to be useful, and does the
organization of main storage make a difference?  (E.g., will I get a
bigger bang for the buck if I add cache to RAIDZ than to mirroring?)

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
Sun Microsystems / 35 Network Drive        71.232W   Vox +1 781 442 2084
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