-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 I have actually witnessed rsync silently corrupting data. But it wasn't rsync's fault. I had a bad RAM DIMM that was corrupting the part of RAM being used as the disk cache. Now I always get ECC RAM.
On 03/11/2014 12:52 PM, Karl O. Pinc wrote: > On 03/11/2014 11:02:28 AM, Sig Pam wrote: >> Hi everbody! >> >> I'm currently working in a project which has to copy huge amounts >> of data from one storage to another. For a reason I cannot >> validate any longer, there is a roumor that "rsync may silently >> corrupt data". Personally, I don't believe that. >> >> "They" explain it this way: "rsync does an in-stream data >> deduplication. It creates a checksum for each data block to >> transfer, and if a block with the same checksum has already been >> transferred sooner, this old block will be re-used to save >> bandwidth. But, for any reason, two diffent blocks can produce >> the same checksum even if the source data is not the same, >> effectively corrupting the data stream". > > Well, yeah. It works that way if you're transferring data over the > network. > > The question is: "how often will this problem exhibit itself?" The > answer is: "Usually, never within the lifetime of the Universe." > > You're a lot more likely to have data corruption due to a cosmic > ray hitting your box. > > There are some cases where the answer is: "Maybe more often." The > only time I can think of that you'd want to worry about is if > you're researching MD5 checksum collisions and have a lot of data > on disk that has collisions in the checksumming. In other words, > if you're actively trying to cause problems it might be an issue. > > (The older rsyncs used MD4.) > > If you're actually _copying_ data rather than backing it up then > avoid the issue by not using rsync. Otherwise the tradeoff is > worth the risk. > > Karl <k...@meme.com> Free Software: "You don't pay back, you pay > forward." -- Robert A. Heinlein > - -- ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~ Kevin Korb Phone: (407) 252-6853 Systems Administrator Internet: FutureQuest, Inc. ke...@futurequest.net (work) Orlando, Florida k...@sanitarium.net (personal) Web page: http://www.sanitarium.net/ PGP public key available on web site. ~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~'`^`'~*-,._.,-*~ -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlMfREUACgkQVKC1jlbQAQeiCACeJnNn9yozItEejG6dWYbp18nS wqQAnRb+wsJFffyPfOVxIGynlpJVYb5t =G4Er -----END PGP SIGNATURE----- -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html