One Last Problem: Lost Writes

Unfortunately, misdirected writes (discussed in the previous lesson) are not the last problem we will address. Specifically, some modern storage devices also have an issue known as a lost write, which occurs when the device informs the upper layer that a write has completed but in fact, it never is persisted. Thus, what remains is the old contents of the block rather than the updated new contents.

The obvious question here is: do any of our checksumming strategies from above (e.g., basic checksums, or physical identity) help to detect lost writes? Unfortunately, the answer is no: the old block likely has a matching checksum, and the physical ID used above (disk number and block offset) will also be correct. Thus our final problem: