Re: Data Deduplication with the help of an online filesystem check

Thomas Glanzmann
2009-04-29T13:58:04Z

Hello Chris,

> But, in your ioctls you want to deal with [file, offset, len], not
> directly with block numbers. COW means that blocks can move around
> without you knowing, and some of the btrfs internals will COW files in
> order to relocate storage.

> So, what you want is a dedup file (or files) where your DB knows a given
> offset in the file has a given csum.

how do I track if a certain block has already been deduplicated?

So, if I only have file, offset, len and not the block number, is there
a way from userland to tell if two blocks are already point to the same
block?

Thomas