Re: disks

[Brendan Kiburg <kiburg@npl.uiuc.edu>]

I don't believe turning off the online analyzer helped at all.  The
run history shows several hours of difficulties before Oleg called Peter
early this morning.  
  I think that actually the biggest change is that somehow the lazy
archiver rate has increased quite a bit. I observed rates as low as 1
MB/sec last night (averaged over several minutes) with fadc on, online
analyer on and both loggers.

  I see rates as high has 7 MB/sec now with lazy archive, lazy lto and
online analyzer ON and fadc-extract off.

  My conclusion also is that we are limited by disk bandwidth.  My plan
for tonight will be to manually delete a chunk of runs that are already on
1 tape (probably tape 23 or 24 depending on our rate problems) and then
find some place/time for the lazy archiver to catch up down the
road.  This should easily buy us 1-2 days.

Best regards,
Brendan


On Sun, 4 Dec 2005, Frederick Gray wrote:

> > I completely agree with your elog. We simply cannot afford
> > to turn off the online analyzer. For mu+ I would
> > turn off the fadc extraction and then one of the
> > lazy loggers. 
> 
> I fully agree that we need the online analyzer as an absolute requirement.
> 
> I am interested to know, however, whether turning off the online
> analyzer actually did increase the archiving rate.  In my model of
> the situation, it would not, since it accesses the data without touching
> the disk.  My impression is that we are limited by disk bandwidth, not
> by the processor load.  Can you confirm this?
> 
> Thanks,
> 
> -- Fred
> 
> -- Fred Gray / Visiting Postdoctoral Researcher                 --
> -- Department of Physics / University of California, Berkeley   --
> -- fegray@berkeley.edu / phone 510-642-2438 / fax 510-642-9811  --
>