My Experience With Bit Rot
Since sometime from 2010, I’ve been using a NAS. My first machine is a 7 bay SOHO NAS made by Thecus - the 7700PRO. All my photos, music, movies and a ton of Animes I’ve collected since my childhood have been transferred from various medium and storage to this NAS.
The N7700Pro faithfully serve my digital content for well over 6 years, until I begin to notice something strange. The data that I copied and CRC32 (later MD5) checksum verified during the transfer stage start to show problems. These problems is usually over in a blank of a eye so I did not really pay much attention to it. The problems include:
- Video corruption. Corruption tend to happen to my MPEG2 encodings the most. In the worst case I can lose a few seconds of audio, video or both, but usually just a bit of corrupted section in a few frames.
- FLAC files will sometimes skip a fraction of a second, a brief moment of silence. If you’re not paying enough attention you may well miss it.
- JPEG files start displaying weird coloured blocks.
Not a lot of files are corrupted. A rough number would be less than fifteen files from tens of thousands, with MPEG2 files (Copied from Video CDs accounting for the majority). This is enough to make me curious to investigate further. Easy enough for FLAC since it has a built in integrity checker.
Comment from: Frank Collins Visitor
I don’t believe bit rot is a problem and the Red Book standard copes with missing bits, to a point.
I store all of my music (FLAC, level 8 compression) on a NAS, using FreeNAS. It does a four-weekly scrub which detects and corrects bit rot on the whole file system. While bit rot isn’t a problem for me, it never will be.
It does a four-weekly scrub which detects and corrects bit rot on the whole file system. While bit rot isn’t a problem for me, it never will be.+1. FreeNAS for the win.
A "single-event upset" was also blamed for an electronic voting error in Schaerbeekm, Belgium, back in 2003. A bit flip in the electronic voting machine added 4,096 extra votes to one candidate. The issue was noticed only because the machine gave the candidate more votes than were possible. "This is a really big problem, but it is mostly invisible to the public," said Bharat Bhuva. Bhuva is a member of Vanderbilt University’s Radiation Effects Research Group, established in 1987 to study the effects of radiation on electronic systems.
Here is an interesting YouTube video about bit flipping.