Re: high load, no bottleneck

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

ED> 2908 getattr
EF> During which timeframe?
ED> 22.9 seconds.
So that's >100 getattrs per second.

> Indeed [lots of 549-byte write requests] is weird.
> But how small write could kill WAPBL performances?
No idea. I think I'm out of luck now, but maybe it rings a bell with someone 
else.

It would probably help finding out (with WAPL logging) how often the journal 
flushes happen.

I myself can't make sense out of the combination of
-- vfs.wapbl.flush_disk_cache=0 mitigating the problem
-- neither the RAID set nor its components showing busy in iostat
Maybe during a flush, the discs are not regarded busy?
Do you have physical access to the server during the test? Then you could have 
a look whether the discs are really idle (as iostat says) or busy (as disabling 
flushing mitigating the problem suggests).

Any experts to explain what exactly "busy" means in the iostat "time" sense?

Maybe also you get some hint by trying to find out whether the problem is NFS 
or client related. Are you able to reproduce it locally? Can you make it happen 
(to a lesser extent, of course) with a single process?