Hard Disk Not Counting Reallocated Sectors
- by MetaNova
I have a drive that is reporting that the current pending sectors is "45". I have used badblocks to identify the sectors and I have been trying to write zeros to them with dd.
From what I understand, when I attempt writing data directly to the bad sectors, it should trigger a reallocation, reducing current pending sectors by one and increasing the reallocated sector count.
However, on this disk both Reallocated_Sector_Ct and Reallocated_Event_Count raw values are 0, and dd fails with I/O errors when I attempt to write zeros to the bad sectors. dd works fine, however, when I write to a good sector.
# dd if=/dev/zero of=/dev/sdb bs=512 count=1 seek=217152
dd: error writing ‘/dev/sdb’: Input/output error
Does this mean that my drive, in some way, has no spare sectors to be used for reallocation? Is my drive just in general a terrible person? (The drive isn't actually mine, I'm helping a friend out. They might have just gotten a cheap drive or something.)
In case it is relevant, here is the output of smartctl -i :
Model Family: Western Digital Caviar Green (AF)
Device Model: WDC WD15EARS-00Z5B1
Serial Number: WD-WMAVU3027748
LU WWN Device Id: 5 0014ee 25998d213
Firmware Version: 80.00A80
User Capacity: 1,500,301,910,016 bytes [1.50 TB]
Sector Size: 512 bytes logical/physical
Device is: In smartctl database [for details use: -P show]
ATA Version is: ATA8-ACS (minor revision not indicated)
SATA Version is: SATA 2.6, 3.0 Gb/s
Local Time is: Fri Oct 18 17:47:29 2013 CDT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
UPDATE:
I have run shred on the disk, which has caused Current_Pending_Sector to go to zero. However, Reallocated_Sector_Ct and Reallocated_Event_Count are still zero, and dd is now able to write data to the sectors it was previously unable to. This leads me with several other questions:
Why aren't the reallocations being recored by the disk? I'm assuming the reallocation took place as I can now write data directly to the sector and couldn't before.
Why did shred cause reallocation and not dd? Does the fact that shred writes random data instead of just zeros make a difference?
