[Linux-cluster] GFS Performance Problems (RHEL5)

[James Chamberlain]

Hi Paul,

I'm guessing from the information you give below that you're using a 
Promise VTrak M500i with 1 TB disks?  Can you confirm this?  I had uneven 
experience with that platform, which led me to abandon it; but I did make 
one or two discoveries along the way which may be useful if they are 
applicable to your setup.  Can you share a little more about your hardware 
and setup?

Regards,

James Chamberlain

On Tue, 27 Nov 2007, Paul Risenhoover wrote:

>
> Sorry about this mis-send.
>
> I'm guessing my problem has to do with this:
>
> https://www.redhat.com/archives/linux-cluster/2007-October/msg00332.html
>
> BTW: My file system is 13TB.
>
> I found this article that talks about tuning the glock_purge setting:
> http://people.redhat.com/wcheng/Patches/GFS/readme.gfs_glock_trimming.R4
>
> But it seems to require a special kernel module that I don't have :(. 
> Anybody know where I can get it?
>
> Paul
>
> Paul Risenhoover wrote:
>>  Hi All,
>>
>>  I am experiencing some substantial performance problems on my RHEL 5
>>  server running GFS.  The specific symptom that I'm seeing is that the file
>>  system will hang for anywhere from 5 to 45 seconds on occasion.  When this
>>  happens it stalls all processes that are attempting to access the file
>>  system (ie, "ls -l") such that even a ctrl-break can't stop it.
>>
>>  It also appears that gfs_scand is working extremely hard.  It runs at
>>  7-10% CPU almost constantly.  I did some research on this and discovered a
>>  discussion about cluster locking in relation to directories with large
>>  numbers of files, and believe it might be related.  I've got some
>>  directories with 5000+ files.  However, I get the stalling behavior even
>>  when nothing is accessing those particular directories.
>>
>>  I also tried some tuning some of the parameters:
>>
>>  gfs_tool settune /mnt/promise demote_secs 10
>>  gfs_tool settune /mnt/promise scand_secs 2
>>  gfs_tool settune /mnt/promise/ reclaim_limit 1000
>>
>>  But this doesn't appear to have done much.    Does anybody have some
>>  thoughts on how I might resolve this?
>>
>>  Paul
>>
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