What does MTBF stand for?

MTBF stands for Mean Time Before Failure. MTBF numbers represent the average number of working hours (when the disk is being used) before the device is expected to fail. Usually the number is in the 100,000s but can go up to 6 or 7 times higher.

Don't misunderstand the number though - its only an average.  Your drive could stop functioning after only days, or even surpass the average by a large amount.  The only real thing that is going to help you is the Warranty.

What does SMART stand for?

SMART stands for Self Monitoring And Reporting Technology.  It is an additional silicon feature on some hard disks, providing a way to learn beforehand if a drive is malfunctioning.  SMART uses techniques to detect bad sector formation, error correction levels, and more. The actual techniques used are up to the manufacturer though, so effects may differ.

What is Thermal Recalibration?

Some parts of the hard disk are vulnerable to heat - enough to affect size or shape temporarily.  Because of this, a common hard disk has built in Thermal Recalibration - where the drive checks itself to confirm and readjust measurements between sectors and tracks.  This method takes time though - enough to cause slight pauses in operation.  For data intensive tasks such as creating CD-ROM's or playing back video, thermal recalibration is not good, causing frames to be dropped or buffer underruns for CDRs.

The only way to really get around the problem is to use large data buffers (common for A/V drives), or bypass it and use completely different methods altogether.

What are Computer Viruses (virii)

Computer Viruses are malignant code and can come up in thousands of ways.  The www.pcguide.com PCGuide sums it up best though: "... in order to be a virus, the program must have the ability to do all of the following:

Run without the user wanting it to and/or create effects that the programmer wants but that the user did not want or request.

Have the ability to "infect" or modify other files or disk structures.

Replicate itself so it can spread to other files or systems.

Most of the time, viruses are destructive - they attempt to damage or replace data on your hard disk. However, that is not the only example of a virus - they can also do something as simple as playing music through your speakers or writing a message on screen.

More to the point, Computer Viruses are always 'Executables', or files that do something only when the computer follows its instructions.    Executables are one of the most commonly used files on any computer, but their only security measure is that *you* have to choose to run it, or choose to automatically let the computer run it, and so on.  You cannot be infected by a virus by simply reading text, because nothing is executed when doing so.

There are several major types of viruses:

Trojan Horses: Aptly named because these are executables which do something the user does not want when used. They typically look like normal executables and when run have the ability to turn other files into Trojan horses.

Worms: Self contained executables. When run, they multiply and spread through networks independently, usually without affecting current data.

Droppers: Self contained Virus delivery systems. They are typically executables that contain data encrypted (scrambled) so that virus scanners cannot tell what is inside. Once they are used, droppers can install and run virus files.

'Macro' Viruses are related to Word Processing programs. 'Macros' are shortcuts - key combinations or scripts designed to do something for you. However, just like normal computer executables, macros are also run as such and can be just as vulnerable.

Viruses are usually structured to attack other executables or your disk's Boot Record.  The Boot Record is code used every time the computer is started up, in order to relay disk information.  Because it has to be loaded every time the computer is on, it makes for a very likely target.  Bootable external disks are also vulnerable for the same reason.

The most recent form of virus attacks your computer's BIOS.  Because most BIOS's are Flash ready (which means they can be overwritten with new information), a successful strike will erase it and leave your computer as unbootable.

How do I combat Viruses?

<Add high risk activities>

Buy an Antivirus program.  They are specifically programmed to sniff out lurking viruses, disassemble and remove them if possible, and delete the infected files if removal cannot be done.  You should also make a point of downloading a new signature file for it often, to keep your system protected.

Quinta, the inventors of OAW technology. www.quinta.com

IBM The inventors of the Hard Disk, Magnetoresistive (MR) and GMR heads. www.ibm.com

Visual RAID guide provides a great multi-page description of RAID levels with nice diagrams to visualize where the data is going. www.acnc.com/raid.html

CIAC Internet Hoaxes has articles about fake viruses and other hoaxes perpetuated over the internet. ciac.llnl.gov/ciac/CIACHoaxes.html

The PCGuide, good specific information on hard disks, viruses, and how they both function. www.pcguide.com

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