[Linux-cluster] Minimum journal size

[Lin Shen (lshen)]

Hi Bob,

How a smaller than minimum journal size (32MB) would potentially affect
the file system? In other words, would it most likely to affect
performance or data integrity? Understanding those will help us to test
It out.

Lin     

> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Robert Peterson
> Sent: Tuesday, February 06, 2007 3:43 PM
> To: linux clustering
> Subject: Re: [Linux-cluster] Minimum journal size
> 
> Lin Shen (lshen) wrote:
> > According to gfs_mkfs man page, the minimum journal size is 
> 32MB and 
> > each node needs at least one journal.
> >
> > Are those hard requirements? Is it possible to lower the minimum 
> > number with some performance reduction? We have a use case 
> that need 
> > to run gfs on a 512MB Compact Flash to share among a few 
> nodes. Based 
> > on the current minimum requirements on journal and resource 
> group, the 
> > disk space overhead is too much.
> >
> > Lin
> >   
> Hi Lin,
> 
> You can create a gfs file system with journals smaller than 
> 32MB by using the undocumented, unrecommended, unsupported -X 
> option (expert mode).
> Something like this: gfs_mkfs -X -J 16 ...
> 
> This gfs_mkfs option is mostly used for testing weird file 
> system conditions.
> I haven't studied the journal code well enough to know if 
> this will work, and if it does, how well it will work.  Use 
> it at your own risk.
> 
> Regards,
> 
> Bob Peterson
> Red Hat Cluster Suite
> 
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