Re: Q: Why subvolumes?

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On Jul 23, 2013, at 7:27 PM, Josef Bacik <jbacik@xxxxxxxxxxxx> wrote:
> 
> Subvolumes are described as directories simply to make it easier to understand.
> Directories do not change the heirarchy within the file system itself, they are
> simply items in the btree like anything else, they are not special at all.
> Subvolumes are _represented_ as directories, but really the directories are just
> links to subvolumes.  Subvolumes are a completely separate b-tree, it has it's
> own locking, it's own inode numbering and everything.  And this isn't inode
> numbering for the sake of inode numbering, our inode numbers are picked by
> simply being the next largest objectid we can add to our tree.  Since a
> subvolume is it's own tree it's inode numbers start over at the begining.
> 
> So it's not that we can just fork off a directory and snapshot there, because
> it's not a tree, it's just an item.  A subvolume is its own tree, which can be
> snapshotted and locked independantly from the other subvolumes.  Thanks,


I like this, it's useful. Could it be integrated into the Wiki?


Chris Murphy--
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