What is Bit Rot?
Bit rot is the phenomenon of random bits in the data flipping (0 to 1 or vice versa). Although there are many reasons a file might experience bit rot, it is generally caused by some form of degradation of the physical storage media.
Below is an example of a file that has experienced bit rot. As you can see, enough bits have flipped with this image to the point where most of it is unrecoverable.
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Image Before Bit Rot |
Image After Bit Rot |
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How to Protect Against Bit Rot?
Until the introduction of Bit Rot Protection from NETGEAR, the easiest way to protect from bit rot is to use a next-gen file system with multiple devices in a mirrored or parity-raided setup. For example, two devices that are both running on a BTRFS file system. In this case, if a bit is damaged, the file system can detect the damaged checksum (automatically upon reads) and fix it with the correct bit off the mirrored device (or by doing an XOR calculation from the other BTRFS Raided devices).
How Does Bit Rot Protection Work on ReadyNAS
ReadyNAS does not need multiple devices in a mirrored or RAID setup to protect against bit rot. By utilizing NETGEAR proprietary Bit Rot Protection, bits in the data that randomly flip flopped are automatically set back to their correct values meaning that the bit rot is not only detected, but also repaired with only a single ReadyNAS (running 6.2.0 and above).
Typically in a next gen file system (BTRFS for example), bit rot protection works on a single layer of storage - the BTRFS layer. The BTRFS layer can detect when the corruption occurs by continuously checking checksums as they are read and then obtain the correct bit from a MIRRORED or RAID device on the same BTRFS layer.
The main difference between typical bit rot protection found in BTRFS and the enhanced Bit Rot Protection featured in ReadyNAS is that the ReadyNAS performs bit rot protection on 2 layers of storage – the BTRFS layer and the lower MDADM RAID layer. The ReadyNAS can catch corrupt checksum events from BTRFS and then ask the lower MDADM RAID layer to figure out what the correct values are block by block – hence both detecting and fixing the bit rot.
Bit Rot Protection in ReadyNAS OS6 is easily enabled with a checkbox on a per lun and per share basis.
ReadyNAS is by far the most affordable storage product that offers Bit Rot Protection in the world. Bit Rot Protection is a standard feature of the the ReadyNAS OS 6 platform and is enabled on any current generation ReadyNAS device. Competitive products offering this type of protection typically start around $7000.