[Linux-cluster] Bottleneck hunting... (GFS Performance)

[HAWKER, Dan]

Hi Wendy,

Thanks for the info. That sounds quite possible, as many of my users have
been creating snapshots of their source trees onto the GFS fs, so there has
been an awful lot of newly created files on the fs over the past day or two.

Will attempt to get some oprofile outputs tomorrow (now everyone is leaving
for home here in the UK, *sluggish-mode* has abated).

Thanks again

Dan

> -----Original Message-----
> From: Wendy Cheng [mailto:wcheng at redhat.com] 
> Sent: Tuesday, December 12, 2006 3:22 PM
> To: linux clustering
> Subject: Re: [Linux-cluster] Bottleneck hunting... (GFS Performance)
> 
> 
> HAWKER, Dan wrote:
> 
> >
> >The nodes are presently developer boxes, so my users ssh in 
> and compile 
> >software mostly but also using Samba/NFS to access. 
> Samba/NFS is only 
> >running on one node (as I believe neither is cluster-aware without 
> >significant fiddling).
> >  
> >
> You can access NFS over GFS across cluster - that is 
> supported. However 
> we currently have an issue with posix lock not able to get propogated 
> across multiple GFS servers due to a Linux NLM problem.  There is a 
> proposed (NFS-NLM) fix from IBM and University of Michigan 
> that is being 
> looked at. Note that this is a linux NFS issue (all linux cluster 
> filesystems suffer this bug) - directly accessing GFS servers using 
> posix locks *does* work.
> 
> Judging by your application, the performance problem you've 
> seen could 
> be caused by fragmentation (lots of deleted and new created 
> files). We 
> do have a tentative patch that could help with this. If you 
> can captured 
> some oprofile outputs when system is in sluggish mode, we may 
> be able to 
> identify whether our fix could help.
> 
> -- Wendy
> 
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> Linux-cluster at redhat.com 
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> 

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