Wednesday, July 4, 2012

Analysis of Hard Disk Bad Sector - Part 4/5

2. b. Bad sectors expanded has an regional pattern

Bad sectors regional pattern is very difficult to repair, because of bad sectors is a very wide area. Bad sectors expanded has an regional pattern, have two types :
1. Bad sectors which is not accessible (can not read)
2. Bad sectors which can be accessed

1. Bad sectors which is not accessible (can not read)
Bad sectors which is not accessible because there is a very severe bad sectors. Because many sectors that can not be read on the disk. If this problem occurs, there will be a SMART Failure Predicted on Hard Disk.
Bad sectors which is not accessible (can not read). Example; SMART Failure Predicted on Hard Disk
If we make a partition C = 50GB, D = 100GB, 100GB unallocation space. When done install a fresh copy of operating system, system can not function normally, and work hard disks are very slow. Low Level Format, can not repair SMART Failure.
Hard disk above, having SMART Failure Predicted on Hard Disk. So, one reason for the SMART failure is, there are sectors in the disk is unreadable. 
Process of SMART Failure Predicted on Hard Disk

Picture No.1 : Bad sectors beginning at LBA 321 500 268 position
Picture No.2 : Because of bad sectors is not repaired, bad sectors will extend to end sectors
Picture No.3a : SMART Failure Predicted on Hard Disk 
Picture No.3b : When done check disk, found that sectors can not be read.

2. Bad sectors which can be accessed
Bad sectors which can be accessed. There are two possibilities, data can be recovered under normal conditions, and data can be recovered in a damaged condition
Bad sectors which can be accessed. Damage block = 67.8 %
 See the picture below. Scale image HD Tune
Scale Legend and Damage Blocks
Scale Legend
1 block = 15 MB
1 block = 15,000,000 bytes
1 block = 15000000/512 = 29297 sectors

Scale Damage Blocks
Total block = 50 x 50 = 2500 block (vertical x horizontal)
Green block = 805 blocks
Red block = 1695 block
Damaged block = (1695 : 2500) x 100% = 67.8 %
 
If in one block (15 MB = 29297 sectors), there are one or more bad sectors, block in the HD Tune will be colored red

Based on above analysis, it can be concluded:
  1. Damage blocks = 67.8%, does not mean there is damage to sectors, covering 67.8%
  2. Damage blocks (red), not all sectors damage.
  3. Damage blocks (red), data can be saved, in a normal condition/damaged.
  4. Damage blocks (red), does not mean there is damage in sector ....... until end sector.
  5. Damage blocks (red), means that there are bad sectors very close intervals. (Bad sectors the which can be accessed).
  6. Damage block (gray), means that there are bad sectors of ....... sectors until end sectors. Bad sectors which is not accessible (can not read)

SMART Failure Predicted on Hard Disk, is a warning if the hard disk damage is very severe. SMART Failure process, can read here Analysis of Hard Disk Bad Sector - Part 5/5

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