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's going on and how many errors have been found.
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 read/write
surface scan to see if the errors can be fixed. 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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