[Linux-cluster] Re: GFS in RHCS on RHEL5.1

[gordan at bobich.net]

On Wed, 16 Apr 2008, denis wrote:

>>> I was under the impression that installing Red Hat Cluster Suite with
>>> GFS in RHEL5.1 was a "supported" solution, but a colleague informed me
>>> that the GFS version in RHEL5.x is currently a technology preview?!
>> Your colleague is semi-misinformed.
>> GFS1 is stable (and has been for years) and available in RHEL5. GFS2 is
>> tech preview. So if you are deploying a cluster right now, do it with
>> GFS1. GFS2 is not yet recommended for production use.
>
> Thanks for the information. My follow-up question is whether GFS (1)
> tolerates high performance situations (with lots of concurrent writes /
> read access / high number of files)?

As much as any other similar system does. If your heavy writes with lots 
of files are all in the same directory, then you will get contention and 
performance degradation, as writing to a directory (e.g. file creation) 
requires a directory lock. Something like Maildir with few user accounts 
won't perform brilliantly. Maildir with lots of user accounts, isn't too 
bad. There are also tuning parameters you can apply (e.g. lock pruning) 
that help in such cases.

The only way you will know for sure is to try it and see for your 
particular application. If GFS can't handle it despite optimizations, you 
could always try OCFS2 or GlusterFS (please do post back with your 
findings if you get that far, I've not seen a decent real-world 
comparison recently), but if you are after clusterable scalability, then 
your application will likely need to be made/modified in such a way that 
it doesn't trip over issues inherent in clustering (and there will be FS 
lock contention issues with _ANY_ scaleable cluster FS).

Gordan