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How to determine the state of the disk; are read errors the problem?
An explanation of terms used on this page can be found here.

Introduction.

If the surface of the disk is going bad you may lose access to certain files or even an entire volume. Read errors are serious business, it usually means that the disk is going bad and in general read errors are progressive: they will increase until the disk fails. This is however not always the case. It's possible that a small area of the disk has gone bad early in the disk's lifespan. Such areas will be marked and left alone, so you don't even notice they exist.

Certain things may indicate that the disk has read problems:
  • you can't access certain files
  • starting the operating system is taking very long and errors pop up along the way
  • accessing certain areas on the disk takes a long time
  • the disk makes "grinding" noises as it tries to read problem areas
  • the operating system may indicate that it has trouble reading files

If you suspect that read errors are a problem you should verify this before continuing with other repair or recovery actions; if you continue working with the disk while these errors are causing trouble you will decrease the chances of a good recovery.

Finding out if read errors are a problem.

There are a number of ways to determine this:

  • you can check the operating system's log files (you should do this anyway, looking in the log files every now and then is always a good idea)
  • you can run a disk diagnostic routine (a SMART check)
  • you can run a disk surface scan

Running the SMART check.

Download and install DiskPatch. Create the bootable DiskPatch diskette or CD/DVD. Start the PC with this disk and run the Disk Diagnostic. This walkthrough explains how to do this. You can analyze the resulting log file or ask us to do that for you.

Running the disk surface scan.

Download and install DiskPatch. Create the bootable DiskPatch diskette or CD/DVD. Start the PC with this disk and run the Disk surface scan. This walkthrough explains how to do this. During the scan the screen will tell you what is going on and how many errors have been found. Please note that by default DiskPatch will halt the scan when an error is found; this is done to make sure you are alerted. This behavior can be changed (read more about this in the DiskPatch manual). If the amount of errors keeps climbing after you've started the scan you might as well abort; something is very wrong and you will need to take the appropriate action.

Note: the DiskPatch trial version allows you to perform a read-only (non-destructive) surface scan.

So now what?

Running the operations that are described above should give you an idea of the state of the disk. If no read errors were found and if the SMART check didn't find any problems for the disk, you are ready to continue with whatever the next step will be. If you HAVE found read errors you should determine what the next step is going to be:

  • if there were only a few errors (less than 10 or 20) you could try attempting to repair these bad sectors. Run a surface scan and allow DiskPatch to try and fix the bad sectors. Please note that repairing the bad sectors usually means that whatever was in there is lost: you may lose a few files.
    The surface scan walkthrough explains how to do this. You can read more about this in the DiskPatch manual, in the section that explains the disk surface scan.
  • if there were many errors (anywhere from a few dozen to hundreds of bad sectors) you should clone the disk. Cloning will make sure that as much data as possible will be copied from the bad disk while it's still possible to read that data. After cloning you can work on the copied disk to finish recovering the files. In many cases cloning the disk will actually lead to a normally accessible copied disk, so you can safely copy files to safety without having to worry about whether your actions will make the problem disk get even worse.
    The disk clone walkthrough will explain how to do this. You can read more about this in the DiskPatch manual, in the section that explains the clone operation.

Links:

Download DiskPatch
DiskPatch manual
DiskPatch manual, section about "disk surface scanning"
Disk surface scanning walkthrough
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