The recovery techniques that we described assume that blocks are written atomically to disk. However, a block may be partially written when power fails, with some sectors written, and others not yet written.

a. What problems can partial block writes cause?

b. Partial block writes can be detected using techniques similar to those used to validate sector reads. Explain how.

c. Explain how RAID 1 can be used to recover from a partially written block, restoring the block to either its old value or to its new value.