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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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