Slideshow:
Intro: Process to update data stored on disk
Intro: Process to update data stored on disk
Intro: Process to update data stored on disk
Overview: Intermittent read failure due to
electrical interference
Overview: Write failure due to
power failure
Overview: Media decay due to
prolonged usage
Overview:
Disk crash
- The process
to update some
data stored on
disk:
- A disk block
of data is
first read into
the main memory:
- User application(s) can then
update
some of the data in the
block in
main memory:
- Finally, the
updated data
is written back to
disk:
Fact:
- A number of circumstances can result in update failure
- A disk block
of data is
first read into
the main memory:
- Types of failures:
- Intermittent read failures:
-
Due to electrical fluctuations
(= interference),
a disk read
operation
failed
Result::
- Data on disk is correct,
- Data in the memory is corrupted
-
Due to electrical fluctuations
(= interference),
a disk read
operation
failed
- Write failures :
- A power failure occurs
during a
disk write operation
Result:
- Data on disk is corrupted,
- Data in the memory is lost
- A power failure occurs
during a
disk write operation
- Media decay:
- A sector
(part of a
block) is
worned
Result:
- Data on disk is lost
- The affected disk block can no longer be used
- A sector
(part of a
block) is
worned
- Disk crash:
- The disk head
has scratched the
platter(s)
Result:
- All data on disk is lost
- The disk head
has scratched the
platter(s)
- Intermittent read failures: