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| Troubleshooting Hard Disk Drives | Errors
My hard disk has bad sectors or is developing bad sectors over time
Explanation: The hard disk (through disk checking utilities) is reporting that one
or more of its sectors are bad. This may be on a new drive, or there may be bad sectors
showing up on a drive that has been in a system for a while.
Diagnosis: Unsurprisingly, bad sectors are generally a real problem with a hard
disk and usually imply a legitimate problem with the hard disk itself. There are
configuration problems that may be responsible, and these are usually resolved pretty
easily, however the usual problem is the drive itself. Bear in mind that IDE/ATA and SCSI
drives, at least all of the ones produced in the last five years or so, use a technique
called remapping or spare sectoring
to hide bad sectors detected on the drive at the factory. A new hard disk should have zero
bad sectors on it. An older drive may "grow" a bad sector or two now and again,
however in many cases this is a harbinger of impending disaster with the disk. Take it as
the warning sign it is.
Recommendation: The steps below discuss possible problems that can lead to a bad
sector showing up. In addition to trying to eliminate the cause, you also should contact
your hard disk manufacturer's technical support
department (phone or web site) and inquire about a utility to remap the bad sector so it
is hidden and replaced with one of the spares on the disk (fixing the cause of the bad
sectors is important but that doesn't get rid of the ones that are already there in some
- As soon as you see any bad sectors show up on a disk that contains data, make
sure you back up the disk immediately, or you risk possible loss of your data. I
would avoid making any significant changes to the software setup on the drive, or adding
any new data to it, until you get the situation resolved.
- Make sure that you have not set the hard disk timing (PIO mode) too high for the drive. You
may want to try reducing the timing and seeing if this resolves the problem. Make sure
that if your system does not support independent
device timing, that you do not have the PIO mode set for what is optimal for the
faster of two devices, but too fast for the slower one.
- Make sure that you are not using an IDE
cable that is too long. The specified maximum is 18 inches, but some drives need them
to be even shorter than that to work properly. Try replacing the cable with a shorter one,
- If you are getting bad sectors on more than one disk in the system, or even after
replacing the disk, then the problem lies somewhere other than the disk, most likely.
Suspect incorrect BIOS settings, and
I would troubleshoot the motherboard as well. It
could even be bad power from the power supply.
- Some hard disks have firmware
problems. In this case the manufacturer may make a firmware upgrade available for the
disk; this is like a flash BIOS
upgrade for your hard disk (except it is easier to install and is used only for fixing
bugs). Check your manufacturer's web site for more information on this possibility. I know
for example that this has happened with some of Western Digital's Caviar series hard disks
and in many cases the firmware upgrade resolved the problem nicely.
- Try to make sure that you have eliminated any of the possible configuration gotchas that
can lead to problems with bad sectors. If you do and are still getting more bad sectors
showing up, the drive should be treated as imminently failing and you should contact your
manufacturer's or system vendor's technical support department. If the drive is new or the
system is still under warranty, insist on a replacement drive. See here for more. There is no reason for a new hard
disk to have bad sectors on it, period. Don't let them try to convince you otherwise.
- If you have a drive out of warranty that gets one or two bad sectors, then if you feel
comfortable with the drive, map out the bad sectors and continue using it. In some cases,
there is just one weak area on the disk, and the rest of it will continue to be quite
usable for some time. However, if the number of bad sectors is large or is increasing in
time, look out, because the chances of the drive failing outright become much higher when
- On very old drives--meaning before IDE, the older drives from the mid-80s that used
stepper motors--there is a phenomenon called "Monday morning blues" that can
result in bad sectors showing up on hard disks. This occurs especially when the hard disks
are cold, after being off overnight or over the weekend (thus the name). These stepper
motor drives cannot compensate for thermal expansion of the disk platters and may not be
able to read the tracks on the drive until the disk has warmed up. Waiting a half-hour may
see the problem go away, but in the long run the disk will need to be low-level formatted again. (None of
this applies to modern IDE or SCSI hard disks).
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