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

Sander
2009-05-06T15:16:26Z

Heinz-Josef Claes wrote (ao):
> Am Dienstag, 28. April 2009 19:38:24 schrieb Chris Mason:
> > On Tue, 2009-04-28 at 19:34 +0200, Thomas Glanzmann wrote:
> > > Hello,
> > >
> > > > I wouldn't rely on crc32: it is not a strong hash,
> > > > Such deduplication can lead to various problems,
> > > > including security ones.
> > >
> > > sure thing, did you think of replacing crc32 with sha1 or md5, is this
> > > even possible (is there enough space reserved so that the change can be
> > > done without changing the filesystem layout) at the moment with btrfs?
> >
> > It is possible, there's room in the metadata for about about 4k of
> > checksum for each 4k of data. The initial btrfs code used sha256, but
> > the real limiting factor is the CPU time used.
> >
> > -chris
> >
> It's not only cpu time, it's also memory. You need 32 byte for each 4k block.
> It needs to be in RAM for performance reason.

Less so with SSD I would assume.

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