[Linux-cluster] GFS RG size (and tuning)

[Mark Hlawatschek]

We did some system profiling and measured the influence of the lkbtbl_size and  
rsbtbl_size values (dlm config parameters) to the cpu usage. We noticed, that 
with large number of dlm locks, these values have a measurable impact to the 
system performance. 
You might want to have a look at 
http://www.open-sharedroot.org/Members/marc/blog/blog-on-dlm/red-hat-dlm-__find_lock_by_id/profile-data-with-diffrent-table-sizes

Mark

On Saturday 27 October 2007 14:57:26 Jos Vos wrote:
> On Fri, Oct 26, 2007 at 07:57:18PM -0400, Wendy Cheng wrote:
> > 1. 3TB is not "average size". Smaller RG can help with "df" command -
> > but if your system is congested, it won't help much.
>
> The df also takes ages on an almost idle system.  Also, the system often
> needs to do rsyncs on large trees and this takes a very long time too.
>
> In <http://sourceware.org/cluster/faq.html#gfs_tuning> it is suggested
> that you should then make the RG larger (i.e. less RGs).  As this requires
> shuffling aroung with TB's of data before recreating a GFS fs, I want to
> have some idea of what my chances are that this is usefull.
>
> > 2. The gfs_scand issue is more to do with the number of glock count. One
> > way to tune this is via purge_glock tunable. There is an old write-up in:
> > http://people.redhat.com/wcheng/Patches/GFS/readme.gfs_glock_trimming.R4
> > . It is for RHEL4 but should work the same way for RHEL5.
>
> I'll try.  I assume I can do this per system (so that I don't have to
> bring the whole cluster down, only stop the cluster services and unmount
> the GFS volumes per node)?
>
> Any chance this patch will make it into the standard RHEL-package?
> I want to avoid to maintain my own patched packages, although as long
> as gfs.ko is in the separate kmod-gfs package that's doable.
>
> --
> --    Jos Vos <jos at xos.nl>
> --    X/OS Experts in Open Systems BV   |   Phone: +31 20 6938364
> --    Amsterdam, The Netherlands        |     Fax: +31 20 6948204
>
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-- 
Gruss / Regards,

Dipl.-Ing. Mark Hlawatschek
http://www.atix.de/
http://www.open-sharedroot.org/

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