Slideshow:
Preparation to handle media decay
Recovering from a media decay failure
Recovering from a media decay failure
- Replacing bad sectors/blocks:
- Preparation:
a disk keeps a
number of
spare blocks:
Disk directory contains:
- A spare block file with a list of spare block numbers
- A bad block file with a list of bad block numbers (initially empty)
- Suppose a
sector in
some disk block
becomes faulty
(due to wear):
Then: this disk block cannot be used to store data
- Solving the
bad block problem:
- We "mark" the bad block as a "bad" block by adding the block number to the "bad block file"
- Replace the bad block with one of the spare disk blocks (so this solution will work even if the disk is full)
- Preparation:
a disk keeps a
number of
spare blocks:
-
Effect
of bad sectors/blocks:
- The disk capacity is reduced....