I ran Crystal Disk Info to look at the SMART information on my external 2 TB drive and it's reporting a "Caution" health status. The specific error is the Current Pending Sector Count, which is 196. I have tried power cycling the drive, and it didn't get fixed. Should I be worried yet? Is this a situation where I should immediately buy another hard drive and back everything up or is there a way to fix it?
Quoting from SecurityNow! podcast number 81:
STEVE: The problem is, and in fact the reason that we’ve always used the slogan “SMART is dumb” at GRC, is we see dead drives all the time where the SMART system says, oh, everything’s fine.
LEO: It’s all working, no problem.
STEVE: Exactly. The drive can die spontaneously while SMART is completely happy and sees nothing going wrong. At the same time there are drives which look like they’re on their last throes from a standpoint of the SMART data that just keep on going for years.
Long story short, you cannot rely on SMART data in any meaningful way. If you want to play it safe, back up your data, if you want to be really safe, back up and get a new drive.
As you can see here, a warning in Current Pending Sector Count indicates potential bad sections.
For those high density disks, a bad sector can spread really soon, so you should start backing up now.
Current Pending Sector Count
Count of "unstable" sectors (waiting to be remapped, because of read errors).
If an unstable sector is subsequently 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.
Basically the drive has detected that sectors could not be read and as such has been marked as potentially unsafe with the intention of either retrying the read at some later point (and putting it back into use if it succeeds) or remapping it with one of the store of reserved spare sectors the next time it is written to.
That high a number does not look like a good thing to me, it could be a sign of the drive failing. As mentioned SMART is not necessarily a reliable indicator of drive health though some indication that it may be failing is better than none.