On 2017-08-31 17:50, Greg Freemyer wrote:
Let me introduce the term "Archival Backup".
An archival backup in my mind is one designed to still be readable a decade or more after it is made. Most DVDs don't have a 10-year or longer expected lifetime.
Right.
Kodak used to sell CDs made with gold as the medium that was sandwiched in the plastic. It was intended for Archival Backup purposes. The idea was that even if the plastic halves came unglued, the gold would not oxidate, so it was a far more reliable medium.
I remember them, although I have never used them.
There are other archival backup solutions. I often have seen lawyers simply put data on a USB drive and put that in a safe. I'm not sure that is a great solution, but it certainly is one that is used frequently.
Safe from stealing ;-) Manageable. I'm unsure about long term, though.
I personally take important large data sets, then put them in the equivalent of a large segmented tar archive. I put a copy of the segments on at least 2 drives. I also record the hash of each of the segments. Then, if I have to use that data in the future, I verify the hashes.
I assume they are not compressed.
I have had occasions where I had hash disagrees on both copies, but fortunately just on a few of the segment files and I was able to piece together a full set without any hash disagrees.
I haven't gone to triple redundancy in general. But arguably it would be smart.
Also, hash disagrees are far less common with drives made in the last 5 years than they were with drives made around 2005. I remember a lot of issues with hash disagrees in the 2005-2010 timeframe.
You could use an archival method that stores with extra data recovery chunks, so that recovery of a damaged sector is possible. One such possibility is "par2", which currently is only packaged on some home repos. But I find it somewhat cumbersome to use. The commercial "rar" includes this feature (since decades ago) and is easy to use. The caveat, of course, is that it does not support the full Linux file metadata set: permissions, attributes, acls, etc. Perhaps one could include a text script in the archive that would recreate them. I saw some other archivers that claim to have it but are betas or young products. I still need to investigate them more. -- Cheers / Saludos, Carlos E. R. (from 42.2 x86_64 "Malachite" at Telcontar)