[DRBD-user] Identifying High iowait on DRBD Computers - SOLVED

Robinson, Eric eric.robinson at psmnv.com
Sat Feb 19 18:29:24 CET 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Bart,

> I have to agree it's an ugly deal when iperf gives good 
> results. Puts it's validity as a good performance measurement 
> tool into perspective.

The problem was not with iperf, but with my assumption that the iperf
tests I ran a week or month before the problem were still valid. If I
had re-run the iperf tests WHILE the problem was occurring, I think the
source would have become evident instantly. Totally my own fault.


> Another pointer might have been the error counters in 
> ifconfig for that interface.

Yeah, that became clear to me as well. And yet another might have been
the 'pe' counter in /proc/drbd on the primary showing the number of
pending requests to the slave. On a healthy system, it is probably
always at or near 0. I bet if I had known what to look for, I would have
noticed some astronomically high number.

I guess the good news is that since I figured all this out the hard way,
I won't soon forget it. Thank you once again,  School of Hard Knocks.
:-)

--Eric





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