5 ms·
Back when hard disks were expensive and CD-R(W) discs (relatively) cheap, I used to do backups and move less used stuff to CD's. A number of years later when th
by jabl 10y ago
Back when hard disks were expensive and CD-R(W) discs (relatively) cheap, I used to do backups and move less used stuff to CD's. A number of years later when this was no longer true (and CD's were becoming laughably small) I moved all the data back to hard drives. In the process I discovered that a fairly large fraction of the discs had developed some minor corruption. Luckily I was able to recover the vast majority thanks to GNU ddrescue ( https://www.gnu.org/software/ddrescue/ https://www.gnu.org/software/ddrescue/ ).
The bottom line is that for long term preservation you really need to keep multiple copies, preferably on multiple mediums, and regularly check and recopy them before the medium gets so obsolete you can no longer access it.
(Yes, I realize the article touches factory pressed discs rather than CD-R's although there is a short mention of such discs too)
- chungy 10y agopar2 is another alternative for redundant copies: https://github.com/Parchive/par2cmdline https://github.com/Parchive/par2cmdline It's kind of like RAID for data, and removes the uncertainty that maybe ddrescue wouldn't get an I/O error and just receive and save bad data (it happens). It'd also be capable of repairing damage, up to the redundancy level par2 archives are created at (default is 5%, can go all the way to 100% -- which would mean you don't need any of the original data assuming all par2 files are not corrupt either (which it can also handle...)).
- blackflame7000 10y agoI wonder if there is some sort of archiving software that is able to encode parity bits similar to how RAID5 works in order to help recovery in the event of corruption to part of the disk.
- DanBC 10y agoYou can use WinRAR with zero compression and recovery volumes. This is useful if you have a bunch of little files - you WinRAR them into a single file with recovery volumes, and then you can create a bunch of PAR2 files on top. I'm not saying this is a sensible thing to do.
- arantius 10y agoSee sibling post about PAR2.