OVERVIEW

THE PROBLEM

If you use computers long enough, you will experience (or at the very least know someone who has experienced) a hard drive failure. The loss of a hard drive can be very consternating to the casual computer user, and even aggravating to someone who uses computers daily as a tool required to accomplish their work. The most astute PC user, however, is smug with the knowledge that they've backed up their data, and while having to endure the replacement of a failed hard drive they are not overly concerned about events as all they need to do is to simply restore their backed-up data to a newly installed hard drive.

I should point out at this time that the majority of PC users have developed and nurtured the habit of NOT backing up their data in spite of knowing that one day, and at the worst possible time, they will experience a hard drive failure...thus losing all of their data which they've worked so hard to develop! It must be the embedded "gambler" instinct in us that forces us to take such chances.

You say that you've implemented a daily data back up schedule, and that you've got copies of all your data squirreled away in a fireproof safe located off-site as well as copies located on-site for instant retrieval? Then you may be doing the right things to protect your data. These are, however, extraordinary measures that most of us don't take, especially if we're a small business (or just simply a casual user of PCs at home) with no budget, personnel, knowledge, hardware, or time to implement such rigorous backup routines. I would like to think that most, however, do make an effort to backup at least some of our more critical data on a regular basis. It does seem though, that as hard as we may try, there's always the one file that we really wished we'd backed up that somehow escaped our attention.

Part of the reality of computing life is that even if you perform a daily backup of your data at the end of the day...what happens if you've got six hours worth of data (faithfully saved to your hard drive every 10 minutes) and all of a sudden you are flashed the message on your computer screen relating to a "SMART test failure?" Maxtor and other hard drive manufacturers have implemented SMART hard drive monitoring and testing, which is supposed to detect current or potential problems with the drive BEFORE we experience catastrophic failures. Not all drives have implemented this feature, nor is it 100% reliable in terms of timely notification of potential or immediate failures. Hopefully any hard drive problems will be detected in advance of a catastrophic hard drive failure, providing you with enough time to back up your data. You do have a backup scheme don't you? With an indication of immediate or impending hard drive failure, you've arrived at the data equivalent of "the fork in the road." Do you shut down your PC to avoid damaging what data you do have saved to the hard drive? Do you stop working and backup your data immediately? Can you? Is your data really saved to the hard drive? Hmmm...it's not the end of the day, and you don't have a backup of your current data!

Should that day arrive when you find yourself in this situation, or with a PC that won't boot, one that you can no longer read data from or write data to, you are faced with a real dilemma if you haven't backed up your data, especially if your day-to-day operations are impaired or curtailed.

HARD DRIVE FAILURE MODES

There are numerous ways in which a hard drive can fail. One of the most obvious would be one with smoke billowing forth from a PC that you cannot any longer boot up. Fortunately, this is one of the least likely scenarios you would ever experience. Instead, hard drive problems are more covert in their development and presentation. Here are a few malfunctions that you are more likely to experience:

CATASTROPHIC FAILURES (Physical Damage)

1) Hard drive motor failure: In this case, the hard drive's motor no longer rotates the hard drive platters. This can be the result of frozen motor bearings or a malfunction with the motor circuit itself. This type of failure is most catastrophic, and is most expensive when considering recovery of data from the drive. The hard drive would require a new motor installation, and is considered to be a "clean room" operation.

2) Hard drive head malfunctions: There are typically multiple heads built into today's hard drives, each one capable of writing or reading data to or from multiple spinning platters through magnetic pickups located on the end of the head's control arm. These heads are "stepped" across the platters by implementing their motion through control current passing through an electric coil. If the heads themselves become damaged, or the coil electronics cease to function, then the heads will not step in a controllable manner across the platters. As with a malfunctioning drive motor, replacing heads is also an expensive proposition when considering the recovery of data from a hard drive experiencing this type of failure. Again, this type of repair should be performed in a "clean room," and would incur costs accordingly.

3) Hard Drive Electronics: If you've ever seen a hard drive's "motherboard," you'll notice that there is an abundance of electronic components packed into a rather small space. These components perform data Input/Output (I/O) functions to and from the computer's data bus, buffers the data, steps the heads across the platters, and controls data flow to and from the spinning platters. Advanced electronics in some also provide hard drive status indicators (Smart notifications) to the PC concerning the hard drive's health. Failures of any of these components can also be catastrophic. If the hard drive's electronics have failed, then depending upon the hard drive construction and the location of the hard drive's motherboard, repair may or may not require a clean room facility. However, you'll still have to conjure up a replacement hard drive motherboard, one hopefully having the SAME firmware version as was used with the original motherboard! Not having the same firmware versions can result in further damage to your data stored on the hard drive.

BENIGN FAILURES (Logical Damage)

1) Corrupted Partition Definitions: A hard drive partition can be defined as the part (or all) of a hard disk that is dedicated to a particular operating system or application and accessed as a single unit. Each hard drive is formatted with at least a single "partition," referred to as the "primary partition." While a hard drive can have as many as four primary partitions, there is normally only one primary partition per hard drive.  This partition is most often labeled as the "C" drive when the hard drive is connected to the PC motherboard's "Primary IDE" port and the hard drive jumper settings are set to "Master." If you have a hard drive with more than one partition, the extra partitions are created in a special partition called the "Extended" partition. You can have only one extended partition per hard drive. Logical drives are created in the extended partition. If you lose (or scramble) the hard drive's Master Boot Record (MBR) located in the first sector of every hard drive, you've lost the information that describes the drive's partitioning scheme, and thus your ability to gain access to your file information. Software data recovery methods, as opposed to mechanical/electrical repairs made in a clean room, can be employed to possibly recoup this data. Software (logical) recovery actions are less expensive obviously than are mechanical/electrical interventions.

2) Deleted Files: When you "delete" a file, the file's data is actually still available on the hard drive, and remains there until you overwrite it with data from a either a newly created file or a modified file saved back to the hard drive...or you otherwise take extraordinary measures to erase it. One or more characters of the filename are modified in order to indicate to the file system that a particular file has been "deleted." By changing the filename structure back to a legal and recognizable filename, you can regain access to this file through your system's file manager. You must be careful NOT to write additional data to your hard drive until AFTER you recover the file(s) in question. In summary, it is possible to overwrite the file's content area on the hard drive with new data, as when you'd save a new file to the hard drive, thus destroying your ability to recover the deleted file with any fidelity at all. Software data recovery methods can be employed to possibly salvage deleted files.

3) Deleted or corrupted MFT file: Microsoft's NTFS (Windows NT, 2000, XP) file system sees any data on a hard drive existing as a file. A hard drive's Master File Table (MFT) is an index of every file on the hard drive. This data can also possibly be recovered using software data recovery methods.

4) Deleted or corrupted FAT file: Windows 95, 98, and ME uses the File Allocation Table, or FAT, file system. The FAT is used to keep track of which hard drive clusters are allocated to a particular file. FAT data can be recovered in some cases as well using software (logical) data recovery techniques.

In summary, any corruption of the following record types can result with problems booting up your PC to begin with or in accessing your data files should you be able to boot up your system: MBR record, NTFS Boot Sector record, FAT Boot Sector record, MFT record, NTFS Folder record, FAT record, FAT Folder record, and/or LINUX's Ext2FS SuperBlock records. These types of records (and thus your data files) can possibly be recovered  using software (logical) data recovery techniques, a relatively less expensive data recovery process, as opposed to having to rebuild the drive...a hardware (physical) solution that is more costly in nature but for which there may be no alternative.

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Last Updated: October 14, 2009