On Friday 07 July 2006 16:52, Jon LaBadie wrote:
>  Granted the inode for a changed file has to be
> copied, but I don't see why the data blocks do.

Which is, in fact, what happens. LVM snapshots are implemented at the device 
level, not the filesystem level, which means copy-on-write takes place 
whenever the filesystem driver (not the user) writes a particular block out 
to disk. "data block" in this context does not mean "blocks containing file 
data", but rather "blocks containing filesystem data, which may include file 
data or file metadata".

The particular question of which blocks will be allocated will depend on the 
semantics of the filesystem in question, of course. Deleting a file, for 
example, may include changes to any number of blocks, depending on how the 
filesystem manages its directory structures.

Cheers,

--Ian
-- 
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