Drive Concepts

The first step in understanding hard drives is to learn the basic concepts involved. Many of the terms covered in Chapter 16 also apply to hard drives, but the additional performance requirements and operating demands placed on hard drives have resulted in an array of important new ideas. In principle, a hard-disk drive is very similar to a floppy drive—a magnetic recording media is applied to a substrate material, which is then spun at a high rate of speed. Magnetic read/write heads in close proximity to the media can step rapidly across the spinning media to detect or create flux transistions, as required. When you look closely, however, you can see that there are some major physical differences between floppy and hard drives.

Hard Drive Failure – Symptoms and Troubleshooting

The hard-disk drive (HDD) evolved to answer the incessant demands for permanent high volume file and data storage in the PC. Early floppy disks provided simple and inexpensive storage, but they were slow and programs quickly became far too large to store adequately on diskettes. Switching between multiple diskettes also proved to be a cumbersome proposition. By the early 1980s, hard drives had become an important part of PC architecture and helped to fuel further OS and applications development. Today, the hard drive is an indispensable element of the modern PC. The hard drive holds the operating system, which boots the system, stores the multi-megabyte applications and files that we rely on, and even provides “virtual memory” for systems lean on RAM. Hard-drive performance also has a profound effect on overall system performance. As you might imagine, hard-drive problems can easily cripple a system. This chapter presents the technology and principles of hard-disk drives, and provides you with some solutions for drive testing and troubleshooting.

Power-Mode Definitions

Modern hard drives are not simply “on” or “off.” They operate in any one of several modes, and each mode makes different power demands on the host system. This is particularly important because today’s PCs are becoming ever-more power conscious, so the ability to control drive power is an integral part of PC power-conservation systems. Typical hard drives operate in any of five different power modes: Spin-up The drive is spinning up following initial application of power and has not yet reached full speed. This demands about 14 W and is particularly demanding of the power supply (if the supply is marginal or overloaded, the hard drive might not spin-up properly).

 
- Seek This is a random-access operation by the disk drive as it tries to locate the required track for reading or writing. This demands about 8.5- to 9.0 W.

 
- Read/write A seek has been completed, and data is being read from or written to the drive. This uses about 5.0 W.

 
- Idle This is a basic power-conservation mode, where the drive is spinning and all other circuitry is powered on, but the head actuator is parked and powered off. This drops power demands to about 4 W, yet the drive is capable of responding to read commands within 40 ms.

 
- Standby The spindle motor is not running (the drive “spins down”). This is the main power-conservation mode, and it requires just 1 W. It might require up to several seconds for the drive will leave this mode (or spin-up) upon receipt of a command that requires disk access.

Platters and Media

Where floppy disks use magnetic material applied over a thin, flexible substrate of mylar (or some other plastic), hard drives use rugged, solid substrates, called platters. You canclearly view the platters of a hard drive . A platter is traditionally made of alu

Smart Command Set

Some of the newest hard drives use the Self-Monitoring Analysis and Reporting Technology (SMART) command set. SMART-compliant drives improve the data integrity and data availability of hard-disk drives by regularly checking for potential drive problems. In some cases, a SMART-compliant device will predict an impending failure with sufficient time to allow users to backup their data and replace the drive before data loss occurs.


Drive Testing and Troubleshooting

Hard-disk drives present some perplexing challenges for computer technicians and every day users alike. The problem with hard drives is that they are inaccessible devices. Unless you have the cleanroom environment to open the sealed drive platters, it is pointless to even consider replacing failed drive mechanics. Even if you could open a drive safely, the advances in hard-drive technology have been so fast and furious that no spare parts market has ever developed. Drive manufacturers themselves rarely bother to repair faulty drives or invest in specialized drive-testing equipment. Clearly, the course for hard-drive repair is to identify defective drives and replace faulty units with new (usually better) ones.Fortunately, not all hard-drive problems are necessarily fatal. True, you might lose some programs and data (backup your hard drive frequently), but many drive problems are recoverable without resorting to drive replacement. Instead of focusing on repairing a hard drive’s electronics or mechanics, today’s repair tactics focus on repairing a drive’s data. By reconstructing or relocating faulty drive information, it is often possible to re.


The important thing to remember when using this workaround is that you must keep a record of the translation values used so that they can be re-entered if the contents of CMOS RAM are lost, or if the drive is moved to another system. Write the values on masking tape and stick the tape on the drive itself. cover from a wide variety of drive problems. Before you begin any sort of drive troubleshooting, you should take the following steps:
Gather a DOS boot disk or Windows 95 startup disk (refer to the end of Chapter 3). If you don’t have a boot disk on hand, you should make one before continuing.

 
- Gather your DOS installation disk(s) or Windows 95 CD-ROM—if you need to reinstall the operating system, these will be invaluable.

 
- Gather any hard drive/controller diagnostics that you’ll need.

 
- Backup as much as you can from your hard drive(s) before attempting any sort of drive service.

Hdd-Controller Bios Error Codes

There might be times when your hard-drive controller fails or cannot communicate properly with the hard drive. When this occurs, you’ll often find that the controller returns an error code. Table 17-9 lists a selection of HDD controller error codes that are Troubleshooting “DOS Compatibility Mode” Problems
One of the great advantages enjoyed by Windows 95 is that it operates in the “protectedmode”— that is, drivers and software can be executed beyond the traditional “real-mode” RAM limit of 1MB. By comparison, DOS is a real-mode environment. DOS programs and drivers can only be executed within the first 640KB of RAM (the “conventional memory” area). If Windows 95 cannot establish protected-mode operation for a drive, it will fall back to real-mode driver support. This is known as DOS compatibility mode. Unfortunately, real mode support often impairs system performance. If you notice that one or more of the hard drives in a system is using DOS compatibility mode (there might be an error message such as: “Compatibility mode paging reduces overall system performance”), you’ll need to track down and correct the cause. In general,
Windows 95 might invoke the DOS compatibility mode for any of the following reasons:

 
- A questionable device driver, TSR, or computer virus has hooked the INT 21h or INT 13h chain before Windows 95 loaded.

 
- The hard-disk controller in your computer was not detected by Windows 95.

 
- The hard-disk controller was removed from the current configuration in Device manager.

 
- There is a resource conflict between the hard-disk controller and another hardware device.

 
- The Windows 95 protected-mode driver is missing or damaged.

 
- The Windows 95 protected-mode driver detected incompatible or unsupportable hardware. You can use the following procedure to isolate and correct the cause of DOS compatibility mode problems:

 
1. If the driver name listed as causing the DOS compatibility mode is: MBRINT13.SYS, your computer might be infected with a boot-sector virus or you are running real-mode disk overlay software (for an IDE hard disk with more than 1024 cylinders) that is not compatible with Windows 95 protected-mode disk drivers.

 
• Run a recent anti-virus program to detect and remove boot-sector viruses (such as Norton Anti-Virus, NAV). You might need to rewrite your boot sector using a DOS command, such as FDISK /MBR.

 
• If you cannot detect any virus activity, check the disk-management software. Be sure that you’re using Disk Manager 7.0 or later (use Disk Manager 7.04 if you’re running DriveSpace 3, included with the Microsoft Plus! pack).

 
2.  Open the Control panel, double-click the System icon, then choose the Performance tab in the System properties dialog. You can identify which drive is using DOS compatibility mode and why.


3. If the driver name that is listed is in the CONFIG.SYS file, contact the driver’s manufacturer to determine whether there is a more recent version of the driver that allows protected-mode operation in Windows 95. You might be able to download the latest driver version from the driver manufacturer’s Web site. If no driver is listed on the Performance tab, check that the hard-disk controller is listed in the Device manager. If not, install it through the Add new hardware wizard. If the wizard cannot detect the controller automatically, run the wizard again, but do not let it attempt to detect the hardware in your computer—instead, select the controller specifically from the hardware list. If your particular controller is not listed, contact the manufacturer of the disk controller to obtain a Windows 95 protected-mode disk driver (or a Windows 3.1x 32-bit disk access (FastDisk) driver, if available).

 
4. Load SYSTEM.INI into a text editor and check to see if the MH2BIT.386 driver is being loaded (check for a line that reads: “device=mh32bit.386”). This driver is installed by MicroHouse EZ-Drive software, and is not compatible with the Windows 95 protected mode disk drivers. Unfortunately, this driver is not removed by Windows 95 Setup, so you’ll need to disable the line manually, save your changes, and reboot the PC.

 
5. If the hard-disk controller is listed in the Device manager, but has a yellow “!” over
it, there is a resource conflict (IRQ, I/O, DMA, or BIOS address range) with
another device, the protected-mode driver is missing or damaged, or the Disable all
32-bit protected- mode disk drivers check box has been selected in File system
properties.

 
• Doubleclick the System icon in the Control panel, click the Performance tab, then click File system. Select the Troubleshooting tab and see that the Disable all 32-bitprotected- mode disk drivers check box has not been selected.


• Resolve any resource conflicts with other devices in the system .


• Check that the protected-mode driver is in the Windows\SYSTEM\IOSUBSYS directory and is loading properly. To find which driver is providing 32-bit disk access, click Properties for the disk controller in Device manager and click the
Driver tab to see which driver files are associated with the controller. For most IDE, EIDE, and ESDI disk controllers, 32-bit disk access is provided by the ESDI_506.PDR driver. For SCSI controllers, Windows 95 often uses SCSIPORT.PDR and a “mini port” (or .MPD) driver. Restart Windows 95, press <F8> when the “Starting Windows 95” message appears, then select a “Logged” (BOOTLOG.TXT) start. If the 32-bit driver is listed as loading properly, you’re all set. Otherwise, the driver might be missing or damaged—try reinstalling the respective 32-bit drivers.

 
6.  If all else fails, you might be able to achieve protected-mode support from the disk controller by disabling any of the controller’s advanced features (i.e., caching, fast or “turbo” modes), or reducing data-transfer rates. You might also try systematically disabling advanced IDE controller features in the CMOS setup.

 
7. If problems persist, you might have to replace the drive controller with a model that better supports protected-mode operation.

Symptoms and Solutions

Now it’s time to take a look at some problems and solutions. The important concept here is that a hard-drive problem does not necessarily mean a hard-drive failure.