Thread: Diagnosing Bad Hard Drives

Why do hard disks die?

There are many, many reasons why data can become corrupted or unusable on your hard disk. Hardware failure in other components (especially memory), poorly written software, viruses and improper shutdown of the system can all result in messed-up data. This is why you should always make backups of your data. Of all the reasons though, the actual mechanical failure of the hard drive is the most inevitable and catastrophic.

How Hard Drives Can Fail

A hard disk drive is composed of one or more platters, spinning disks containing tracks of magnetic information. These platters are read by read/write heads that hover just above the surface of the disk on a cushion of air created by the speed of the platter's rotation. These heads are attached to an armature that can move them over the surface of the disk, powered by a magnetic 'voice coil'.

The whole assembly moves incredibly quickly and precisely. The platters generally rotate at either 5400 or 7200 RPM, and the movement of the read/write heads to separate areas of the disk is almost instantaneous.

Hard disks will fail eventually because they are mechanical devices, and as such, wear out. It's as simple as that. The most likely reason for a drive to fail before its time, however, is physical damage. If a drive is bumped or jostled while it is active (meaning that the read-write heads are busy reading or writing data on the surface of the platters) there is a chance that the heads will make contact with the surface of the platter, which can cause all sorts of problems.

This 'head-crash' can cause damage both to the read heads and the surface of the platter, can knock the read-heads out of proper alignment, and a host of other badness.

Fortunately, modern drives are well protected against this kind of damage while the heads are in motion. All hard drives manufactured in the last decade or so protect themselves automatically when the drive spins down by parking the read-write heads, or lowering them onto a safe area on the surface of the stopped platter.

A stopped drive is extremely difficult to damage by physical means. For this reason, you should avoid moving your computer around while it is powered on. Obviously, most laptop hard disks are better protected than standard 3-½ inch desktop hard drives, but they can still be affected by physical force.

The electric motor that powers the platter's rotation is also subject to failure over a long period of use. A failure in the drive's motor or bearings can cause slow performance or data read/write errors due to the platters spinning up slowly or rotating at an incorrect speed.

Hard drives contain filtered air-intakes, to provide the internal atmosphere needed to keep the read/write heads hovering above the surface of the disk. A failure in the filtering can allow particles into the drive mechanism, which can quickly cause great damage to your data.

Any mechanical failure of the disk, or physical damage inflicted to it will almost certainly cause attendant software problems, generally due to bad sectors.

What do bad sectors mean?
A bad sector is a sector of the disk to which data cannot be written. This may be due to a number of reasons, but to your operating system all that matters is that it can no longer use that portion of the disk. If the disk has yet to be used, or is being reformatted, bad sectors are not really an issue. All recent operating systems map a drive's bad sectors and avoid them while formatting it for use.

Modern hard drives are manufactured with 'spare' sectors which are only used to replace space lost due to bad sectors. This allows a drive to automatically compensate for any slight manufacturing defects which may have resulted in the drive having bad sectors 'out of the box.' When formatting a drive, bad sectors are detected and these 'spare' sectors are used to replace them as necessary.

Where bad sectors become an issue is when previously usable sectors become damaged due to disk error. Any data on these sectors is in danger of being corrupted or destroyed. The operating system has no way of automatically compensating for this loss, potentially leading to data corruption on a larger scale and system instability if the affected data was crucial.

Bad sectors can be created by software errors, or slight errors in the read/write heads which cause the data laid down on that particular sector to be completely illegible, and thus appear as bad to the operating system. This type of 'soft' bad sector can generally be fixed by completely erasing the disk (by writing every sector over with a pattern of zeroes).

Bad sectors created by a mechanical error have a tendency to breed more bad sectors quickly. Since the margin for error inside a working disk is so slim, any surface damage or debris created by a mechanical failure or 'head-crash' will quickly cause more damage as it interferes with the read/write heads. When formatted, a drive with 'hard' bad sectors like these will use the spare sectors to as much as possible replace the existing bad sectors as detailed above. Of course, if the bad sectors are still spreading due to loose particles or surface errors in the disk, the disk will still be unstable. At this point, the only option is to salvage as much data as possible from the drive before it dies completely.

Fortunately there are ways to fix or work around bad sectors on a disk.

Hard disk checking and repair methods

There are three main methods of testing and fixing the integrity of your drives and your data. We will look at some applications that perform these tests a little later in the guide.

Error checking is the process of scanning the files and folders present on your drive, searching for corrupt files and inconsistencies. For example, deleted files which the file system still contains entries for, or files which are referenced more than once. This can clean up basic file problems which might be causing data issues on your disk. If you constantly experience errors while performing error checking it could be a sign that your drive is dying, and bad sectors are proliferating. Error checking takes very little time to carry out.

A surface scan examines each sector of the disk in detail in order to identify and mark bad sectors. These areas of the disk can then be marked off-limits to the file system, and spare sectors used to replace them. Surface scans typically take a large amount of time to perform, but are the only non-destructive way to map out any bad sectors on your drive that have developed since you last formatted it.

SMART diagnostics test: A SMART test queries the internal SMART (Self-Monitoring, Analysis and Reporting Technology) information of your drive for its current status. This serves as a test of your drive's current physical well being. We'll get into the benefits of using SMART next, but first, what are the warning signs of a failing hard drive?

Warning signs to watch for
While you may be able to repair software errors caused by bad sectors, and in some cases you may be able to repair the bad sectors themselves, if your drive has begun to fail mechanically nothing will stop the process.

The catch then is to detect the imminent failure of your drives before they give out on you and data is lost. Let's look at some common warning signs of impending hard drive failure:

Frequent but irregular crashes, especially while booting up Windows.
Frequent and cryptic error messages while performing typical activities like moving files.
Folder and file names that have been scrambled and changed.
Disappearing files and folders.
Really loo....ong waits to access folders and files.
Hard disk is silent for a long period after you request data by opening a file or folder.
Garbled output from open files or printing.
Hard drive grinds away constantly because of noisy bearings.
Any of the above signs mean you should check your drive using one of the utilities we detail below as soon as possible.

Sound can be an excellent indicator of disk trouble. If you previously didn't hear a peep from your hard drive, but now you do... Check it. If it seems much louder than usual, or makes occasional clicks or grinding sounds... Check it ASAP and be prepared to backup your data and replace the drive.

If your drive is making regular clicking or grinding sounds, chances are you have a mechanical failure within the drive. Turn off your PC as soon as possible, as this kind of problem can quickly snowball into a huge headache that is way beyond the scope of a pair of Aspirin. The longer the drive is powered on, the more damage you may be doing to your data.

SMART: What it is and what it does

SMART stands for Self-Monitoring, Analysis and Reporting Technology. This capability is standard on all modern hard drives, and provides each device with a degree of internal status monitoring. Used in conjunction with software, this can alert users to the impending failure of the disk.

The BIOS (Basic Input/Output System) of most computer motherboards contain SMART monitoring software which can interpret the information from drives attached to the system and warn of potential trouble. However, this function is generally disabled by default since it slightly adds to the boot up time of the system.

The SMART monitoring system built into your computer's BIOS is rudimentary, usually only capable of telling you whether or not the drive is 'OK' based on the conclusion of its internal SMART diagnostics. The more advanced analysis features of this monitoring system can be accessed by using a drive analysis program that can fully query the drive's status.

SMART works by comparing a hard drives current performance in a number of areas to its ideal parameters. For example, the time it takes a drive to spin up to speed in order for data to be read from it is recorded by the SMART monitor and compared to the factory rated time. A discrepancy here could indicate problems with the motor or the bearings. SMART monitors up to 30 separate attributes of the disk (the actual number varies depending on how the manufacturers of both the drive and the motherboard have implemented the system).

It is advisable to turn on your computer's SMART monitoring option if you are worried about the status of your hard disks. This feature can be accessed though the system's BIOS settings page. To access this, press DEL repeatedly immediately upon powering up your system. Some manufacturers use other keys (like F2, or F6) or key combinations to access the BIOS. This information should be presented in the manual or on the POST screen of the system. SMART options are generally found within the 'advanced BIOS options' section of the BIOS.

Note that SMART is by no means reliable when it comes to predicting drive faults. First of all, it analyzes the physical attributes of the disk only, nothing else. SMART's effectiveness also depends on the way monitoring in implemented on your motherboard. There is no real standard for which SMART attributes should be monitored, or even what acceptable thresholds are. These variables are up to the manufacturer to provide, so there in no universal standard set of values. SMART should always be used in conjunction with a more in-depth disk monitoring tool.

Hard disk diagnostic tools


Let's take a look through some of the tools you can use to diagnose drive troubles before they become terminal.

Windows Disk utilities: CHKDSK

The CHKDSK utility included with Windows XP can perform both quick and surface scans.

You can launch the utility from Windows by opening 'my computer,' right clicking on the hard drive you wish to test and selecting 'properties' then from the 'tools' tab, select 'check now.'

Open the command prompt by going to 'start/run' and typing 'cmd.'

From the command prompt, type 'chkdsk /v (the drive letter you wish to check):' and hit ENTER. CHKDSK will do a quick scan of the drive, then inform you if it found any errors.

Now run 'chkdsk /R (same drive letter): to perform a full surface scan for bad sectors and fix any errors. Chances are you will be requested to restart the computer in order to carry this out, since the utility needs exclusive access to the disk in order to do a surface scan and fix errors.

Once you have restarted and CHKDSK has carried out the surface scan, Windows will boot normally. For a log of the results, right-click 'my computer' and select 'manage,' then open up 'event viewer\applications'.

Look for the most recent event from the 'winlogon' source and double click it to open the log. All the details about the operation CHKDSK just performed, including any bad sectors found, will be in here.

CHKDSK is all the program you need to perform quick tests or surface scans of your drives. Many Windows commercial drive diagnostic packages actually use CHKDSK to perform their testing 'under the hood.'

Manufacturer Produced Hard Drive Utilities

The major hard disk manufacturers like Maxtor and Seagate all offer diagnostic software designed to support their drives. These packages generally meet two specifications: 1) they are quite comprehensive and effective and 2) Tend to be less than easy to use:

Maxtor's Powermax (If the link fails, just search for "powermax")

Seagate's Seatools

Western Digital's Data Lifeguard Diagnostics

If you have found a problem with your drive and wish to send it in for warranty service, the major manufacturers will generally insist on you testing your drive with their utility first. Only then will you receive an RMA number to ship the drive with.

Most of these utilities require installation on a floppy disk or CD, then ask you to boot off that medium.

Of these companies, Western Digital's Windows-capable Data Lifeguard Diagnostics is the only program which will willingly scan the drives of other manufacturers. In fact, this program is also extremely easy to use and performs error checking, surface scans and SMART diagnostics. Let's take a look at how to use it:

First, install and run the program.



The main screen shows all available physical and logical drives. Double click the physical drive you wish to test.

From here, 'quick test' will do the basic file and folder integrity check, 'extended test' will perform a surface scan of the drive, and 'write zeros' will fully or quickly erase all the data on the disk. Click the 'SMART status' column of the drive you wish to test to see a full SMART diagnostic list.

HDD Diagnostic Software

Next up on our list of hard drive diagnostic software is DiskCheckup, a free SMART diagnostic tool. DiskCheckup by Passmark Software is an easy to use, basic SMART diagnostic tool for your hard disks. It communicates with each disk and retrieves its current status and compares it to the ideal profile for the drive.

Simply run DiskCheckup from the .exe file, select the hard disk you wish to scan from the drop down box and click 'get info.'

Other Utilities for checking the status of a suspect hard drive include Active Smart , which is a Window-based SMART monitoring program. Essentially "Active Smart" does the same thing as DiskCheckup, which we profiled above, but with many more bells and whistles.

Active Smart checks your drives current performance against its ideal performance and gives you a graph of the results in each category.

Once you have started up the program, double click one of the drives in the top windows to see Active SMART's opinion of your drive's health. The difference between the threshold (red) line and the green current attribute line should tell you all you need to know.

Diagnostic Software con't

Active SMART will notify you if an attribute line changes on a later scan, so you can track your drive's health over time.

The program has a variety of scanning options, but the default will scan your drives during Windows startup, and every hour after. The actual scanning process is almost instantaneous.

Active SMART is trialware, with a 21-day period. Consider this a good basic tool for diagnosing the physical status of your drives. While it does not actually do anything that DiskCheckup does not, its automatic scans, notification options and easy to read graphs make for a more useful program.

HD Workbench by DIY Data Recovery is another comprehensive trialware program you may also want to look into.


Lastly, there is Symantec's popular Norton Utilities software suite includes Disc Doctor, which analyzes partition tables and data on the disk for errors. It actually uses Windows XP's integrated CHKDSK program to do the scanning, but it gives you much more verbose information on what errors were found and fixed. It's certainly worth running for a quick test of your data's integrity on the hard drive.

Fixing bad sectors - the last resort

If your drive has become unusable due to data errors and none of the above utilities seem to help, there are a couple of possibilities. One: your drive has mechanical errors, and will shortly only be useful as a fridge magnet , or two: you have a virus or major software error that is causing 'soft' bad sectors to be created. In either case, your first step should be to get as much of your data off the drive as possible. See PCStats Guide to backing up data and data recovery for help on how to do that.

Once you have salvaged your data, you can attempt to 'zero-fill' the drive, by writing 0 values to every single sector of the drive. This can accomplish what normal formats and partitioning can't, since it erases the entire disk - so best to double check that all your data is off the drive before starting this procedure.

If your errors were being caused by software problems, this may well fix the disk, and allow you to reinstall you OS back onto it freshly, or put it back in service for storing data. On the other hand, if your drive has mechanical problems, this will not help.

The best way to 'zero-fill' your drive is by using the option within the diagnostic software made by your hard disk manufacturer. Western Digital's Data Lifeguard Diagnostics can also carry out this operation on all drives, though since this is a Windows program you will have to move the afflicted hard drive to another computer if it is a system drive.

In conclusion, be aware of the status of your hard drives. You know better than anyone how your computer system normally operates, so when you start seeing (or hearing) strange errors and inconsistencies, it's time to think about protecting your data. While there is no way for a user to save a mechanically failing hard disk, it is easy to save your precious data if you act fast. Better yet, back it all up now, so you don't have to worry about that curl of smoke that may be emanating from your drive next week.

We recommend that you back up your essential data frequently, and take a little time each week or month to test your hard disks for errors.