On Fri, 30 Oct 2015, Richard PALO wrote:
I sort of like the dtrace iosnoop so I'm using the following to see the
*W*rites to sd4
(which is my rpool device)... hope this is actually saying what I'm
experiencing;-)
$ pfexec /opt/DTT/iosnoop -dsd4 -va |grep -w W |& tee $HOME/rpool-iosnoop.log
there is a wave every 15 seconds or so, here is a minutes taste with a gate
build in the background:
Even one updated byte in the zfs transaction group interval will
result in multiple writes to the pool devices when the transaction
group commits.
Take a look at using the script "/opt/DTT/FS/fsrw.d". This one shows
I/O at the filesystem and device level. If the issue is being caused
by paging, then also look at "/opt/DTT/FS/fspaging.d ".
On my almost idle system, I am seeing some writes to
"/etc/svc/volatile/init-next.state". Since this file does not
normally exist, I assume that it becomes
"/etc/svc/volatile/init.state" or is otherwise a transient file.
Depending on the needs of your system, you might try tuning zfs
transaction groups so they happen less frequently.
Bob
--
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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