[CentOS] determining correct size for LV copy operations

Wed Apr 30 20:43:23 UTC 2008
Kai Schaetzl <maillists at conactive.com>

I have some problems with copying LV volumes and determining correct size.
For instance, if I want to copy an LV from one machine to another. I dd 
the LV to a file on the other machine, then dd the file to the new LV.
That fails, because a few MB are missing.

  LV Name                /dev/VolGroup01/LogVol01
  LV Size                4.62 GB

  LV Name                /dev/xenvm/lvmtest1
  LV Size                4.62 GB

Both were created with lvcreate -L 4.62GB, but there's obviously a small 
rounding or whatever difference. The size of the physical extents seems to 
be different.

I can determine the size of the output file
-rw-r--r--  1 root root 4966055936 Apr 30 21:19 lvmtest1.img

That is 4849664K which is the smallest size unit that lvcreate accepts.
lvcreate -L 4849664K --name lvmtest1 xenvm - and then it fits.
But I hope there's a better way to determine the *exact* size?


Kai Schätzl, Berlin, Germany
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