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Disk A and disk B both contain file SomeFile. On disk B this file has rotted. When reading the file SomeFile into memory, the read will be distributed among t
by Wicher 9y ago
Disk A and disk B both contain file SomeFile.
On disk B this file has rotted.
When reading the file SomeFile into memory, the read will be distributed among the disks (for performance reasons) (and it will probby need to span a multiple of the stripe size).
Ok, file is read into memory, including the bitrotted part from disk B.
Now we write the file blocks back - as one does.
Voila! Both disks now contain the bitrot. And mdadm will not complain - disk A and B are identical for the area of file SomeFile.
- IgorPartola 9y agoMoreover, even if you don't read the file, and the bit rot is discovered during the monthly compare, at least on Linux the disk that is considered correct will be chosen at random. So you need at least three disks to have some semblance of protection. Have you guys seen many laptops that come with three or more drives? Just use ZFS. Even on a single disk setup you will at least not get silent bit rot.