[Linux-cluster] Minimum journal size

[Robert Peterson]

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