[Linux-cluster] gfs 6.1 superblock backups

[Bob Peterson]

On Tue, 2008-06-03 at 13:27 -0500, Chris Adams wrote:
> Bob and Wendy, 
> Thank you for your input on this.  What I am trying to do 
> is upgrade a GFS 6.0 filesystems which are attached to various 
> RHEL3/CentOS3 systems.  After performing the steps which outline the 
> process of going from 3 to 4, but on a CentOS 5 system, I get the problems 
> mentioned in my message yesterday Re: /sbin/mount.gfs thinks fs is gfs2?  
> Everyt time I reinstalled a system with CentOS 5 and tried to get gfs 
> running again I got the same error.
> 
> Since I know that this is an unsupported operation, I haven't sought 
> support for this.  However, I noticed that my upgraded filesystem had 
> sb_fs_format = 1308.  The mount code checks for sb_fs_format == 
> GFS_FORMAT_FS for gfs 6.1 and GFS2_FORMAT_FS for gfs2.  Since it was 
> neither of these, it kept dying saying that it was a gfs2 fs when mounting 
> it as gfs, and vice versa.  Manually modifying sb_fs_format allowed it to 
> mount immediately afterward.  A subsequent gfs_fsck completes all passes 
> successfully.  
> 
> Is that sufficient for upgrading the filesystem if the other steps are 
> performed?  All fs operations appear to be successful at this point.
> 
> thanks,
> -chris

Hey Chris,

I really don't know offhand what changed in the file system between the
RHEL3 proprietary version of GFS and the version we have today.
(There aren't any differences between RHEL4.x and RHEL5.x GFS format).

I can't think of a good reason why my predecessors would have changed
the file system format ID unless there was something in the file system
that changed and needed reorganizing or reformatting.  So like you, that
makes me concerned about some loose end.  However, I do know gfs_fsck
pretty well, and if it says the file system is sane, you should be able
to trust it.

This is just a guess, but perhaps it had something to do with the
difference between the old proprietary GFS (i.e. the old license file)
and the GFS Red Hat open-sourced (i.e. empty license file because no
license is needed to use it).  If I'm correct, it's not likely to
cause any problems.

There are a few developers from that era around; maybe they'll remember
what changed back then and post why it was done.

Regards,

Bob Peterson
Red Hat Clustering & GFS