[CentOS] determining correct size for LV copy operations

Thu May 1 11:31:07 UTC 2008
Kai Schaetzl <maillists at conactive.com>

John R Pierce wrote on Wed, 30 Apr 2008 13:56:32 -0700:

> I'd probably use dump ... | restore ...   to copy it, assuming its an 
> e2fs/e3fs on that logical volume.   then the volume sizes are immaterial.

Well, these are mostly xen volumes with xvda. It's indeed the difference in 
physical extent. I can check the size of the PE with vgdisplay. Most vg's 
have 4MB, but the ones on small disks have 32MB (which is a bit surprising, 
I would expect the opposite). Then I can check with lvdisplay the actual 
number of extents and multiply that with the PE size. Gives me a difference 
of 4 MB. So, I better set the PE size on small disks in the future. And for 
existing volumes I can use -l instead of -L which sets the size in physical 
extents and not in bytes.


Kai Schätzl, Berlin, Germany
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