On Aug 17, 2009, at 12:24 PM, Roman Naumenko <no-
re...@opensolaris.org> wrote:
I have a strange filing that attached slog device doesn't do
anything on zpool.
zsan0store 203G 10.7T 47 23 5.85M 2.49M
raidz2 203G 10.7T 47 22 5.85M 2.44M
c7t0d0 - - 25 5 830K 418K
c7t1d0 - - 25 5 830K 418K
c7t2d0 - - 25 5 829K 418K
c7t3d0 - - 25 5 829K 418K
c7t4d0 - - 25 5 830K 418K
c7t5d0 - - 25 5 830K 418K
c7t6d0 - - 25 5 830K 418K
c7t7d0 - - 25 5 830K 418K
... c9d0 128K 29.7G 0 1 2 229K
... c9d0 128K 29.7G 0 0 0 79.1K
... c9d0 128K 29.7G 0 0 0 0
format -e
. c9d0 <FiD 2.5-90429AAB00000000-0001-29.84GB>
/p...@0,0/pci-...@1f,2/i...@0/c...@0,0
As a back-end storage I use raw volume created on a raidz2 pool with
Comstar iscsi. Initiator is a standard windows iscsi. Speed and
latency is tolerable on 118b, especially with compression=on and
128k bsize on zfs.
The question is about zfs slog device and how to check if it can
improve access.
Does zfs cache raw volume data on slog device or only on a filesystem?
What kind of tests I can run to see it works?
The slog will cache all synchronous writes on the zpool whether they
be zfs or zvol writes.
While running a synchronous write look at the output of 'iostat -x 1'
locate the 'sd' representing the slog device and look at it's io.
-Ross
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