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

Thomas Glanzmann
2009-04-28T20:15:53Z

Hello Chris,

> Yes, but for the purposes of dedup, it's not exactly what you want.
> You want an index by checksum, and the current btrfs code indexes by
> logical byte number in the disk.

that would be good for online dedup, but in practice that is not going
to work or I don't see how.

> So you need an extra index either way. It makes sense to keep the
> crc32c csums for fast verification of the data read from disk and only
> use the expensive csums for dedup.

I think that this should be part of a userland programm. It can take all
the time it wants during weekends to find dedup blocks.

> > Does that mean that I can dedup 4k blocks even if you use extents?

> Yes.

Perfect. :-)

Thomas