Hello! On Tue, Jun 19, 2007 at 08:04:57AM -0400, Chris Mason wrote: > On Tue, Jun 19, 2007 at 10:11:13AM +0100, Pádraig Brady wrote: > > Vladislav Bolkhovitin wrote: > > > > > > I would also suggest one more feature: support for block level > > > de-duplication. I mean: ... > > > That would be very usable feature, which in most cases would allow to > > > shrink occupied disk space on 50-90%. > > > > Have you references for this number? > > In my experience one gets a lot of benefit from > > the much simpler process of "de-duplication" of files. > > Yes, I would expect simple hard links to be a better solution for this, > but the feature request is not that out of line. I actually had plans > on implementing auto duplicate block reuse earlier in btrfs. One problem with hard-links for me is, they also share the meta-data, especially file permissions and owners. Take a Subversion checkout for example: For each file "$A" Subversion saves a backup under ".svm/text-base/$A.svn-base" for file comparison and diff generation. The user controls the file permissions of "$A", Subversion protects its backup with 0444. You can't hard-link them, because than "svn diff" doesn't work anymore if your editor doesn't break the hard-link, or worse, your permissions can get wrong. If previous versions Subversion also had an extra file for file attributes (mime-type, permissions, to-be-ignored, etc.) Since most files had no special attributes, each had a file only containing "END". Those you could hard-link by hand to save space. If somebody want to research this further: There is this nice little package called "perforate", which contains "finddup" to find duplicate files. Run it two times, once with "-i" to ignore permissions while comparing file contents finddup -i -d / and once without "-i" for "content and permissions must match" finddup -d / This will give you a hint on how many files you could hard-link or how many files share their content. BYtE Philipp -- / / (_)__ __ ____ __ Philipp Hahn / /__/ / _ \/ // /\ \/ / /____/_/_//_/\_,_/ /_/\_\ pmhahn@xxxxxxxxxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
