Mailing List Archive: Netapp: toasters

missing ops? messages file and `qtree stats` data inconsistency

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tmerrill at mathworks

Oct 2, 2009, 10:28 AM

Post #1 of 2 (404 views)
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missing ops? messages file and `qtree stats` data inconsistency

So, I'm comparing the /etc/messages lines that report ops:

Fri Oct 2 03:00:00 EDT [XXXXXX: kern.uptime.filer:info]: 3:00am up 38 days, 19:46 4097331567 NFS ops, 121286775552 CIFS ops, 60 HTTP ops, 0 FCP ops, 0 iSCSI ops

with the output of qtree stats:

Volume Tree NFS ops CIFS ops
-------- -------- ------- --------
vol1 qtree1 261704 212370168

Volume Tree NFS ops CIFS ops
-------- -------- ------- --------
vol2 qtree2 372425752 37601
vol2 qtree3 26190085 56

I'm collecting the output of `qtree stats` every hour on the hour,
to match up with the data output in the messages file.

Diff'ing the data on an hourly basis shows that the qtree stats
are accounting for about 2/3'rds of the ops on the toaster. Said
another way, the data output in the messages file is about 50%
higher than the qtree stats.

I've checked and double-checked that there is no data, except for
/etc, that is not in a qtree. No volumes have been onlined/offlined
in the time interval and the filer hasn't been rebooted nor have
the qtree stats been zero'ed.

So...why the discrepancy? Does qtree stats not count the same
ops as the line in the messages file?

Until next time...

The MathWorks, Inc. 508-647-7000 x7792
3 Apple Hill Drive, Natick, MA 01760-2098 508-647-7001 FAX
tmerrill[at]mathworks.com http://www.mathworks.com
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tmerrill at mathworks

Oct 2, 2009, 10:56 AM

Post #2 of 2 (363 views)
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Re: missing ops? messages file and `qtree stats` data inconsistency [In reply to]

On Fri, 2 Oct 2009, Jeff Mohler wrote:

> Qtree stats are ONLY reads and writes.
>
> No metadata ops (readdir, etc, etc, etc...wafl IO..etc..etc.etc..even
> CIFS has gobs of metadata ops, just like NFS)

Jeff, we were thinking similarly as well...

I compared the output of the three following stats, 60 seconds apart,
and clearly the qtree stats is the smallest of the three:

qtree stats 972297
cifs stat 2396439
uptime 2395260

However, given our workload, we have tons of CIFS getattrs, and a small
fraction of reads or writes. So, I think our suspicions are true (not
all ops are reported by qtree stats) but the specific excluded ops in
our case seem to still be off.

Hrmph.

Until next time...

The MathWorks, Inc. 508-647-7000 x7792
3 Apple Hill Drive, Natick, MA 01760-2098 508-647-7001 FAX
tmerrill[at]mathworks.com http://www.mathworks.com
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