If you suspect that that your iPod’s hard drive has started to fail:
Take your iPod and place your right thumb on the centre SELECT button and your left on the top MENU button. Press down both thumbs for about 6 seconds until your iPod reboots. Immediately move your left thumb around to the rewind button |<< on the left and hold this down together with SELECT for a further 6 seconds. Your iPod should now switch into Diagnostic Boot mode. Press MENU for Manual Test, then select IO > HardDrive > HDSMARTData to reveal your stats. For comparison here are mine taken when my 6th Generation Classic was about 2 years old:
Pending Sectors: 0
PowerOn Hours: 2202
Temp: Current 24c
Temp: Min 10c
Temp: Max 50c
Take a note of your results. When finished press MENU+SELECT for 6 seconds to reset the iPod again.
With modern disc drives sectors are no longer marked bad by a disc scan, if the SMART firmware detects a sector it has trouble accessing it will attempt to invisibly reallocate it to a spare area of the disc.
Note that I’ve only 12 remapped sectors and none pending. To help explain what the numbers mean here is an extract from the Wikipedia S.M.A.R.T. article:
Reallocated Sectors Count
Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks this sector as “reallocated” and transfers data to a special reserved area (spare area). This process is also known as remapping, and “reallocated” sectors are called remaps. This is why, on modern hard disks, “bad blocks” cannot be found while testing the surface – all bad blocks are hidden in reallocated sectors. However, as the number of reallocated sectors increases, the read/write speed tends to decrease. The raw value normally represents a count of the number of bad sectors that have been found and remapped. Thus, the higher the attribute value, the more sectors the drive has had to reallocate.
Pending sector count
Number of “unstable” sectors (waiting to be remapped, because of read errors). If an unstable sector is subsequently written or read successfully, this value is decreased and the sector is not remapped. Read errors on a sector will not remap the sector (since it might be readable later); instead, the drive firmware remembers that the sector needs to be remapped, and remaps it the next time it’s written.
Large numbers of Reallocs or Pending Sectors would suggest your drive is failing and that you may need to repair or replace your iPod. Check your stats after another attempt to update your iPod. If the numbers increase that again points to hard drive failure. While it won’t be good news at least you’ll know it isn’t some random software problem and you can decide what to do next.