Charles,
Just like UNIX, there are several ways to drill down on the problem. I
would probably start with a live crash dump (savecore -L) when you see
the problem. Another method would be to grap multiple "stats" commands
during the problem to see where you can drill down later. I would
probably use this method if the problem lasts for a while and drill down
with dtrace base on what I saw. But each method is going to depend on
your skill, when looking at the problem.
Dave
On 08/30/10 16:15, Charles J. Knipe wrote:
David,
Thanks for your reply. Answers to your questions are below.
Is it just ZFS hanging (or what it appears to be is
slowing down or
blocking) or does the whole system hang? <br>
Only the ZFS storage is affected. Any attempt to write to it blocks until the
issue passes. Other than that the system behaves normally. I have not, as far
as I remember, tried writing to the root pool while this is going on, I'll have
to check that next time. I suspect the problem is likely limited to a single
pool.
What does iostat show during the time period of the
slowdown?<br>
What does mpstat show during the time of the
slowdown?<br>
<br>
You can look at the metadata statistics by running
the following.
echo ::arc | mdb -k<br>
When looking at a ZFS problem, I usually like to
gather
echo ::spa | mdb -k<br>
echo ::zio_state | mdb -k<br>
I will plan to dump information from all of these sources next time I can catch
it in the act. Any other diag commands you think might be useful?
I suspect you could drill down more with dtrace or
lockstat to see
where the slowdown is happening.
I'm brand new to DTrace. I'm doing some reading now toward being in a position
to ask intelligent questions.
-Charles
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