S. Alexander Jacobson wrote: >On Thu, 6 Jun 2002, Robert Brockway wrote: > > >>>On Thu, Jun 06, 2002 at 01:30:46AM -0400, S. Alexander Jacobson wrote: >>> >>> >>>>I just joined this list. Two question: >>>>1. Can reiserfs detect that I have two copies of >>>>the same file on disk and store tham as one file >>>> >>>> >>>Hm, you mean, each time you create a file, reiserfs should scan all >>>other files and see if there is exactly a file like you just wrote? >>>Hm, even something more complicated as you are writing to a file in >>>4k chunks. >>>Definitely no. >>> >>> >>And besides, how could it even know whether you even want them to be the >>same or not. >> windows uses a signature.
>> I keen plenty of identical files around (online backups, >>etc) and I'd be mighty upset if the filesystem started hard linking them >>together :) >> >> > >That is why I said lazy copy on write. > This is not patented, it is an old thread, everyone agrees that it should be done, no sponsor at the moment though. > One >implementation would be for the file system to >keep a ref count of how many different files the >user intended. When an applicatiion writes to a >file, the file system checks the ref count. If >the ref count is greater than 1, the file system >copies the file, decrements the ref-count, and >gives the writing application a pointer to the new >copy. > >I'm sure there are smarter implementations, but >the point is that the file system can certainly >differentiate in theory between user hard links >and actual hard links. > >-Alex- > >___________________________________________________________________ >S. Alexander Jacobson i2x Media >1-212-787-1914 voice 1-603-288-1280 fax > > > > > >
