[Lustre-discuss] Lustre SNMP module

[Andreas Dilger]

On Mar 20, 2008  18:32 -0400, Mark Seger wrote:
> >> As a final note, I've put together a tutorial on using collectl in a
> >> lustre environment and have upload a preliminary copy at
> >> http://collectl.sourceforge.net/Tutorial-Lustre.html in case anyone
> >> wants to preview it before I link it into the documentation.  
> >> If nothing else, look at my very last example where I show what you 
> >> can see by monitoring lustre at the same time as your network
> >> interface.  
> >
> > Very good, thanks for this. The readahead experiment is insightful.
> >   
> It was to me when I first encountered the problem.

This is a very interesting example, and I wish we had known about
collectl a year ago before we invested time in writing data gathering
scripts which aren't as useful as what you have here.

One question - is this "over readahead" still a problem?  I know there
was an but like this (anything over 8kB was considered to be sequential
and invoked readahead because it generated 3 consecutive pages of IO),
but I thought it had been fixed some time ago.  There is a sanity.sh
test_101 that exercises random reads oand checks that there are no
discarded pages.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.