[Linux-cluster] journal size, performance

[Christopher Barry]

On Mon, 2007-12-03 at 14:39 -0500, Shawn Hood wrote:
> Hey folks,
> 
> I'm in the process of implementing a GFS cluster.  A quick over of our hardware:
> 
> 1 Apple xraid (with plans to bring the two others into the SAN after testing)SA
> 3 Dell (2x 1950 / 1x 2950) boxes, running RHEL4u5
> Qlogic SANbox
> Qlogic HBAs
> 
> lvscan of SAN volume group
> 
> ACTIVE            '/dev/hq-san/nlp_qa' [700.00 GB] inherit
>   ACTIVE            '/dev/hq-san/prod_reports' [1000.00 GB] inherit
>   ACTIVE            '/dev/hq-san/cam_development' [500.00 GB] inherit
>   ACTIVE            '/dev/hq-san/nlp_development' [500.00 GB] inherit
>   ACTIVE            '/dev/hq-san/svn_users' [1.50 TB] inherit
> 
> 
> We run a mixed environment of RHEL4.5 and RHEL5.1.  We're currently in
> the process of developing a plan to shorten the OS lifecycle so we can
> have all of our cluster nodes in a more homogenous RHEL5.1
> environement.  Anyhow, we plan to scale to about 3-5x our current
> storage capacity and 3-4x our current server count within the next
> several months.
> 
> That said, I need to decide know the parameters to use when creating
> journals--number of journals and size.  I could not find any
> information about how the number of journals affects performance.
> What kind of performance impact would I see by creating 9-12 journals
> that we will eventually need?  If the size of the filesystem is
> smaller than the logical volume, can the number of journals be
> increased?  What about journal size impacting performance?
> 
> If information on this already exists, could someone point me to it?
> 
> Shawn
> 
> --
> Linux-cluster mailing list
> Linux-cluster at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-cluster


Shawn,

I am assuming you do not have a GFS cluster up yet. If you plan on
moving quickly to RHEL5.1, I suggest you do you initial as that version
because the cluster infrastructure is not compatible between 4.5 and
5.1. I do not believe that having both 4.5 and 5.1 in a unified cluster
is a supported configuration.

I do not think unused journals affect performance - they just reserve
space.

man gfs_jadd to see how to add more journals later.


-- 
Regards,
-C

Christopher Barry
Systems Engineer, Principal
QLogic Corporation
780 Fifth Avenue, Suite 140
King of Prussia, PA   19406
o/f: 610-233-4870 / 4777
  m: 267-242-9306