Fresel Michal - hi competence e.U. wrote at about 16:42:50 +0100 on Wednesday, March 23, 2011: > re to Jeffrey J. Kosowsky <backuppc@ko...> - 2011-03-02 15:59 > > If you are changing the appended rsync digest format for cpool > > files using rsync, I think it might be helpful to also store the > > uncompressed filesize in the digest There are several use cases > > (including verifying rsync checksums where the filesize is required > > to determine the blocksize) where I have needed to decompress the > > entire file just to find out its size (and since I am in the pool > > tree I don't have access to the attrib file to know its size). > > > > > re to Jeffrey J. Kosowsky <backuppc@ko...> - 2011-03-03 16:40 > > > Alternatively, if you want the first time hack to work then you could > > make the pool file name equal to: <md5sum>_<SHA-256sum> which would > > still be smaller than SHA-512sum and I would wager that we are > > unlikely ever to start seeing lots of files with simultaneous > > collisions of the md5 and the SHA-256 checksums. In a sense, the > > SHA-256 checksum would act like a unique chain suffix and since it > > would always be there you never would have to actually decompress and > > compare the files to see if a chain is necessary. Plus you then would > > have two essentially independent checksums built into the file name. > > > i would propose to extend it to > <MD5>_<SHA_256>_NULL_<uncompressed_FILESIZE> > by default > > and an option for (if user enables it :) > <MD5>_<SHA256>_<SHA512>_<uncompressed_FILESIZE> > maybe somebody wants to to recalculate the SHA512 sums afterwards (in idle > time?) - therefore the "NULL" in the default name above > > indeed ... this would generate very long filenames:
I don't see the advantage of having SHA256 and SHA512. Let users choose one or the other. The only reason I proposed adding another checksum is if people are worried about MD5 collisions. So the goal would be to pick a 2nd checksum whether SHA256 or SHA512 or any other choice that the user believes to be sufficiently unique. Having the uncompressed filesize may be nice but it is not critical to unique pool naming which after all is the purpose of the checksums. > as for the name-length limit of 255 > 32_64_128_<filesize> > meaning there would be space left for 27 more characters (10^26) > > so we could also append Filesizes of ... uuh ... wait ... > 10^12 - Terabyte > 10^15 - Petabyte > 10^18 - Exabyte .... > well ... very big files :) > > Having all kinds of checksums and sizes already calculated - these > information may be reused for custom user-scripts like > # integration testing of pool using md5, sha256 AND sha512 :) > # appending .sha256 or sha512 files in archive-operations > # post-dump integrity tests on client ... > > Greetings > Mike > > > ------------------------------------------------------------------------------ > Enable your software for Intel(R) Active Management Technology to meet the > growing manageability and security demands of your customers. Businesses > are taking advantage of Intel(R) vPro (TM) technology - will your software > be a part of the solution? Download the Intel(R) Manageability Checker > today! http://p.sf.net/sfu/intel-dev2devmar > _______________________________________________ > BackupPC-devel mailing list > BackupPC-devel@lists.sourceforge.net > List: https://lists.sourceforge.net/lists/listinfo/backuppc-devel > Wiki: http://backuppc.wiki.sourceforge.net > Project: http://backuppc.sourceforge.net/ ------------------------------------------------------------------------------ Enable your software for Intel(R) Active Management Technology to meet the growing manageability and security demands of your customers. Businesses are taking advantage of Intel(R) vPro (TM) technology - will your software be a part of the solution? Download the Intel(R) Manageability Checker today! http://p.sf.net/sfu/intel-dev2devmar _______________________________________________ BackupPC-devel mailing list BackupPC-devel@lists.sourceforge.net List: https://lists.sourceforge.net/lists/listinfo/backuppc-devel Wiki: http://backuppc.wiki.sourceforge.net Project: http://backuppc.sourceforge.net/
