However, when a hard disk fails, the computer doesn't bootââ,¬"as in the case of a boot drive failureââ,¬"and the frenzy to save important company data ensues. When faced with such a problem, don't panic. Just remember these simple troubleshooting tips for hard drives.Seven steps to my troubleshooting process
Here's a quick look at the process I follow when troubleshooting a hard disk. I'll elaborate on each of these points in the proceeding sections. With each point, ask yourself the question(s) that follow.
- Physical connectivityââ,¬"Is the drive receiving power? Is it plugged into the PC by a correctly connected ribbon cable? For IDE drives, are its jumpers set correctly? Or with SCSI drives, are its
- SCSI termination and ID set correctly?
- BIOS setupââ,¬"Does the BIOS see the drive?
- Virusesââ,¬"Does the drive contain any boot sector viruses I need to remove before continuing?
- Partitioningââ,¬"Does FDISK find a valid partition on the drive? Is it active?
- Formattingââ,¬"Is the drive formatted using a file system that the OS can recognise?
- Drive errorsââ,¬"Is a physical or logical drive error causing read/write problems on the drive?
- Operating systemââ,¬"Does your OS have a feature that checks the status of each drive on your system? If so, what is that status?
Checking physical connectivity
To work properly, a hard drive needs power and a connection via a ribbon cable to the PC. If a drive doesn't work after moving it to a new PC, after physically moving the PC, or after the cover has been taken off, start your troubleshooting by checking the physical connectivity. It's possible for plugs to jiggle loose when moving a PC, and it's easy to uproot a ribbon cable connection when pulling circuit boards or performing other maintenance tasks inside the case.
A hard disk works with any Molex connector from the PC's power supply. Make sure the plug is fully inserted. Molex connectors require a lot of pressure to fully insert, and even more pressure to remove, so don't be afraid to push hard or pull, as the case may be. Just make sure you handle the plastic connector, and do not try to push or pull the wires.
As the PC starts up, place the palm of your hand on the flat part of the hard disk. If you can detect any vibration, the drive probably has power. If there's no movement at all, either the drive's physical mechanism is shot or the Molex connector you have selected is faulty. Try using a different connector before assuming the drive has a problem.
Systems like the AT/LPX have a small connector that runs from the front of the case to the hard disk. On ATX systems, it runs from the motherboard to the hard disk. This enables the LED on the case to illuminate when the hard disk is in use. Don't rely on that LED as a positive indicator as to whether or not the hard disk is receiving power, though. The light could be burned out, the wire disconnected, or the drive might be receiving power but not be connected correctly to the PC.
The other physical requirement for a drive is the PC itself. If it's an IDE model, the drive should be connected via a ribbon cable to the IDE bus on the motherboard. Connections can also be made with a SCSI or proprietary expansion card. Secure both ends of the ribbon cable connector and make sure the connector is covering all pins. On systems where the pins are bare instead of surrounded by a plastic ridge, it's easy to offset the connector by a row or two on the pins. If the drive is getting power but the BIOS can't find it, try a different ribbon cable; the one in use might have a broken wire or other flaw.
Author's note
There are two types of hard disk ribbon cables: 40-wire and 80-wire. UltraDMA 66 and above requires the 80-wire cable. If you use the 40-wire type, the drive will be limited to UltraDMA 33 performance.
The red stripe on the ribbon cable must match up with Pin 1 on both the drive and the motherboard or expansion card. Sometimes, though, it's not easy to locate Pin 1. Look for tiny numbers at one end of the connector. If you see a 1 or 2, that's the end with which the red stripe should be matched. Some connectors are notched on one side while the ribbon cables have a tab that fits into that notched area. However, this isn't always the case. Unlike with floppy drives, where the drive light stays on even if you have the ribbon cable backward, there is no simple way to tell whether you have the cable backwards. Without the notched connectors, your only choice is to use the trial-and-error method.
Tip
Don't mount the drive in the computer case until you're sure it works. Sometimes those little screws can be hard to reach, so you only want to mount the drive once. For testing purposes, the hard disk can temporarily sit at an angle, unmounted, but propped up in some way. Don't allow the drive to hang suspended by the ribbon cable or power cable; this puts stress on the cable and can cause broken wires or dislocated connectors.
Checking jumper settings
On an IDE hard disk, one or more jumpers on the drive must be set to determine its Master/Slave status. This setting isn't usually an issue in an existing hard disk installation that suddenly doesn't work anymore, but it can cause problems when you move a drive from one PC to another.
Depending on the drive, the following jumper settings may be available.
- Singleââ,¬"Use this setting when the drive is the only one on that IDE subsystem; that is, the only one on that ribbon cable. Not all drives have a Single setting; if there is none, use the Master setting instead.
- Master (MS)ââ,¬"When there are two drives on the IDE subsystem and the other drive's jumpers are set to Slave, or if this is the only drive on the subsystem and it doesn't have a separate Single setting, use this setting.
- Slave (SL)ââ,¬"Use this setting when there are two drives on the IDE subsystem and the other drive's jumpers are set to Master.
- Cable Select (CS)ââ,¬"If you are using a cable that relies on the device positioning to determine its Slave/Master status, use this setting. This setting is uncommon.
In Figure A, Master has been selected. Jumpers are set with the jumper running up-and-down; setting them side-to-side would be the same as using no jumpers at all.
Figure A
Depending on the drive, the jumper positions may or may not be clearly labeled. There
should be a chart or sticker on the drive showing the positions. If you see neither, try
visiting the drive manufacturer's Web site to see if a diagram is available.
Checking SCSI termination
If the machine uses a SCSI drive, there are two factors with which to be concerned: termination and ID. These settings are not an issue when troubleshooting a drive that has suddenly gone bad in an existing system, but if you are moving a drive from one system to another and it doesn't work in the new system, improper SCSI settings may be the culprit.
If this is the last SCSI device in the chain, it must be terminated. Termination methods vary. On some devices, you set termination with an extra jumper; on others, you use a cap or plug over a connector. On most hard disks, you terminate using a jumper setting.
SCSI-based drives usually have jumpers just like ATAPI ones, but instead of setting the Master/Slave status, they assign a SCSI ID number to the device. Some SCSI devices have a wheel or button instead of jumpers with a little window indicating the setting, but this is uncommon on a hard disk.
There can be up to seven SCSI devices on a single narrow SCSI bus, and up to 15 devices on a wide SCSI bus. There are either eight or 16 addresses in total, depending on your system. The host adapter takes one of those addresses, leaving seven or 15 for the remaining drives. Usually, the host adapter claims the highest number for itself.
The SCSI ID comes from a binary representation of the jumpers. For example, on a device with three SCSI jumpers and all of them are without jumper settings, the ID would be 000b (b stands for binary here), or 0. An ID of 001b would be 1; 010b would be 2; and so on.
The problem lies in the fact that some manufacturers set the jumpers to read from left-to-right, while others use right-to-left. So on one drive, the leftmost jumper set would be 1, while on some other drive, the rightmost jumper set would be 1. Check the drive's label for information about which way the drive works. If all else fails, try the manufacturer's Web site.
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If it's a seven step provess, why are there 8 dot points?