Hi, Say I download a large file from the net to /mnt/a.iso. I then download the same file again to /mnt/b.iso. These files now have the same content, but are stored twice since the copies weren't made with the bcp utility.
The same occurs if a directory tree with duplicate files (created with bcp) is put through a non-aware program - for example tarred and then untarred again. This could be improved in two ways: 1) Make a utility which checks the checksums for all the data extents, and if the checksums of data match for two files then check the file data, and if the file data matches then keep only one copy. It could be run as a cron job to free up disk space on systems where duplicate data is common (eg. virtual machine images) 2) Keep a tree of checksums for data blocks, so that a bit of data can be located by it's checksum. Whenever a data block is about to be written check if the block matches any known block, and if it does then don't bother duplicating the data on disk. I suspect this option may not be realistic for performance reasons. If either is possible then thought needs to be put into if it's worth doing on a file level, or a partial-file level (ie. if I have two similar files, can the space used by the identical parts of the files be saved) Has any thought been put into either 1) or 2) - are either possible or desired? Thanks Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
