HEADS UP: ZFS v28 merged to 8-STABLE

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Fri Jun 10 21:40:22 UTC 2011

On Fri, 10 Jun 2011, Jeremy Chadwick wrote:
> We tried using dedup on one of our systems, but within 10-15 minutes
> turned it off.  I believe the added CPU overhead of dedup was causing
> the system to act "bursty" in other non-ZFS-related tasks; e.g. turn on
> dedup, then in a SSH window hold down the letter "q" indefinitely, then
> in another window do some ZFS I/O.  The "q" would stall for 1-2 seconds
> at times (SSH connectivity was via direct private LAN, so network
> latency was not what we seen).  Without dedup this behaviour wasn't seen
> at all.  I'm happy to try any advice/patches on a locally-accessible
> box (e.g. private LAN, VGA console is right behind me, etc.).

Dedup can require a huge amount of RAM, or a dedicated L2ARC SSD, 
depending on the size of your storage.  You should not enable it 
unless you are prepared for the consequences.

Solaris 11 Express does not admit to supporting dedup even though it 
can be enabled in previous OpenSolaris and is supported in Oracle's 
NAS products (which run a variant of Solaris 11).

Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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