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

[Josh Gray]

I had the same problems this week on GFS only about 800gig of mostly  
small files.  My application did not require it to be mounted on the  
whole cluster concurrently so i went ahead and switched to EXT3 with  
much better performance.

Support said i would probably expect significant improvement with  
more RG's but we went with the other file format before we tried that.

Josh


On Oct 27, 2007, at 8:57 AM, 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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