How should I understand "Current Pending Sector Count" in CrystalDiskInfo reports?

What is Current Pending Sector Count and should I worry about it?

This is a "Potential indicator of imminent electromechanical failure" (row coloured pink in S.M.A.R.T.).

You should back up this disk as it could fail at any moment. Keep an eye on this value and see if it increases.

S.M.A.R.T. Attribute: Current Pending Sector Count

Description

Current Pending Sector Count S.M.A.R.T. parameter is a critical parameter and indicates the current count of unstable sectors (waiting for remapping). The raw value of this attribute indicates the total number of sectors waiting for remapping. Later, when some of these sectors are read successfully, the value is decreased. If errors still occur when reading some sector, the hard drive will try to restore the data, transfer it to the reserved disk area (spare area) and mark this sector as remapped.

Please also consult your machines's or hard disks documentation. Recommendations

This is a critical parameter. Degradation of this parameter may indicate imminent drive failure. Urgent data backup and hardware replacement is recommended.

Source S.M.A.R.T. Attribute: Current Pending Sector Count

• Count of "unstable" sectors (waiting to be remapped, because of unrecoverable read errors).

• If an unstable sector is subsequently read successfully, the sector is remapped and this value is decreased.

• Read errors on a sector will not remap the sector immediately (since the correct value cannot be read and so the value to remap is not known, and also it might become readable later); instead, the drive firmware remembers that the sector needs to be remapped, and will remap it the next time it's written.

  However some drives will not immediately remap such sectors when written; instead the drive will first attempt to write to the problem sector and if the write operation is successful then the sector will be marked good (in this case, the "Reallocation Event Count" (0xC4) will not be increased).

  This is a serious shortcoming, for if such a drive contains marginal sectors that consistently fail only after some time has passed following a successful write operation, then the drive will never remap these problem sectors.

Source S.M.A.R.T.