[Linux-cluster] GFS2 file system maintenance question.

Ryan Mitchell rmitchel at redhat.com
Tue Mar 15 07:09:17 UTC 2011

On 03/15/2011 08:35 AM, Jack Duston wrote:
> I planned to free up enough space on the GFS2 LV to migrate data off 
> one LUN. I could then decrease the GFS2 file system size, remove the 
> LUN from the LV, destroy the RAID LUN, replace 1TB HDDs with 3TB HDDs, 
> rebuild the RAID LUN, add the new larger LUN to the LV, increase the 
> GFS2 file system size, and repeat migrating data off the next LUN.

No you will not be able to use that procedure to swap LUNs.  If you have 
the ability to present the new LUN's before removing the old LUN's from 
the volume group, it would be possible to:
1) vgextend the volume group using the new LUN
2) pvmove the extents from the old LUN to the new LUN
3) vgreduce the old LUN to remove it from the volume group

This could be done 1 LUN at a time.  It doesn't even require you to grow 
the filesystem (unless the new LUN's are larger than the old ones).  
This is common and I've seen it done many times.  You could even use a 
temporary staging LUN to shuffle the data around.

If you do not have the capacity to add additional LUNs before removing 
the original LUNs, then you will face a difficult migration, possibly 
using backup/restore as you mentioned.

The feature to reduce the filesystem has not been implemented; there is 
no code as yet to manage it.  It isn't commonly required.


Ryan Mitchell

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