Bad Cluster, no problem?

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Thread Starter
Nov 6, 2007
Okay, I've been turning off my external hard drive whenever i want to. Lately I've been making back-ups from cds and storing them in my external. Then, I turn it off (bad idea i guess, I should turn it off when my whole computer is off).

I ran checkdisk on it, and it found a "bad cluster" on EVERY backup that I made. Then, it fixed them.

I tested out each backup, but it still works fine!

Now after searching through the forum, a "bad cluster" is basically a dead part of the hard drive. But it seems like I'm not having any problems. Will I have problems in the future?

When you store files on an external, are there temporary files still being run that I can't see?

What's the best way to avoid further bad clusters? (I'm guessing only turn off external when the whole comp is off, or should I never turn it off?)
Apr 10, 2000
Killing the power to an external drive without going through the 'disconnect procedure' runs the risk of data corruption; but, I've never heard of it causing a bad cluster.

Theoretically, a bad cluster is bad surface area on the disk platter. For some reason that cluster will no longer deliver the data written to it. I've heard it explained that the disk could actually be scratched by contact with the read/write head due maybe to a bump it received while it was running. I've also heard it explained that the metal adheared to the surface of the aluminum platters is coming 'unglued' and a microscopic portion has come off.

Then there is a possibility the platters are actually perfect; but, the logic board (the circuit board on the drive) is going bad intermittently, giving the OS false information that the platter is bad.

In any case, if the disk has more than one bad cluster, I would back up my data and replace it immediately.
Aug 1, 2003
I agree that you should consider replacing the drive, especially if the number of bad clusters increases.

If you run chkdsk /r on that drive, it will attempt recovery from bad clusters, mark them so they won't be used, and tell you at the end how many it found.

As far as shutting off the drive without using Safely Remove Hardware-->

The disk has a cache, or temporary memory, and if you have data cached and shut it down before it is written to the drive, the data is lost. That's what "Safely Remove" does--dump the cache to disk.

But there is a fix that will allow you to turn it off anytime you want. Go to Device Manager and find the drive. Look under the Policies tab and find where it says to optimize for quick removal. Basically, that removes the cache so all data is written directly to the drive and you can unplug it or turn it off whenever you want.


The first one will scan for bad clusters.

Free Hard Drive Testing Applications:
HD Tune
HDAT2 (Diagnostics and bad sector recovery)
MHDD Low-level Diagnostics
Bootable Hitachi Drive Fitness Test Floppy or CD Image (works on most drives)

Hard Drive Manufacturers' Diagnostic Utilities Links:
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