Convert ext4 lvm to normal ext4 partition

Patrick O'Callaghan pocallaghan at gmail.com
Fri Nov 12 18:29:52 UTC 2010


On 12/11/10 1:13 PM, Michael Miles wrote:
> Considering that the LVM is a ext4 Virtual partition it seems to me 
> that it would be easy to convert but there is no such beast out there
> Lots of stuff for converting ext3 to ext4 but nothing for what I need.

This is pure speculation on my part, but I'm guessing one reason it's 
hard is that the LVM layer knows nothing about the ext4 layer. The ext4 
layer contains lots of metadata (inodes, freelists, etc.) which includes 
pointers to disk sectors or extents. In a physical partition these point 
to real disk addresses but in an LVM partition they are virtual (compare 
real with virtual memory for an analogy). From LVM's viewpoint the 
entire ext4 fs is just disk sectors with random binary data. The fact 
that some of this stuff is fs metadata and some isn't means that a 
conversion tool would need to understand the ext4 metadata to convert 
it. Of course if it's ext3 or xfs or btrfs etc. then the same applies, 
with different rules for each one.

Worse still, if you want a in-place conversion you have to be able to do 
this in such a way that it's recoverable even after a hard system crash 
in the middle of the conversion. And if you don't need it in-place, you 
already have the solution as said before.

Just my 2 cents.

poc


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