The drive reliability ratings on these pages are based on our own experience with the particular drive model. Nothing else.
Of course, when we are buying hard our own drives we also consider a number of other factors: the track record of the manufacturer, the drive design (not that most are terribly different these days) and the external signs of build quality. In the end though, there is nothing like having 30 or 300 of a particular model out in service. For these pages we consider our actual service failure rates and only our actual service failure rates.
Of course, it's never possible to be 100% sure of the reliability of a drive until it's obsolete. We can estimate the working life of, say, an ST-225 very well, because they came out in 1984 and we have seen hundreds of them over the years. And, yes, a few people were still running them up until quite recently!
Notice that it is easier to assign a poor rating (AA3 or BA) than a good one. If a drive has a very high failure rate, it becomes apparent even with a small sample, but a low or moderate failure rate can only show up with larger numbers.
Also take note that reliability standards change over the years. Do not make the mistake of thinking that because the 1984 vintage ST-225 and the 2001 vintage WD Caviar 400BB are both AA1-rated drives that you could expect to see the same failure rate per thousand shipped! The ST-225 and the 400BB are, however, similar in that both have shown themselves to have low failure rates by the standards of the day. Modern drives give far less trouble than older ones used to, and put up with far worse abuse before they fail. There is not a drive on the market today that would not rate an 'AAA' by 1984 standards, or indeed by the standards of 1994
We don't even try to assess a reliability rating for SCSI drives. We don't see enough to have a fair sample size, and as you would expect from drives that typically cost betwen three and eight times as much as their more humble mass-market siblings, they are probably all in the 'AAA' class in any case.
For all our emphasis on hard drive reliability, actual hardware failure is in fact a rather rare way to loose your data. Even the poorest drives are vastly more reliable than the human beings who operate them. If you have never lost important data through your own stupidity, then you have probably never used a computer, or perhaps just never used one for anything that matters.
The table below lists the main causes of data loss in order of frequency.
| The Four Causes of Data Loss |
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| User Error |
Otherwise known as "Woops!" This is easily the most common cause of lost data. There are many, many ways to do this, ranging from dropping a file on the shredder when you meant to drop it on the printer, to the classic DOS combination:
C:\> DIR A: (nothing important)
C:\> DEL *.* ('oh %#@^$#!')
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| Malicious Damage |
Most people are reasonably virus-aware — though none of us are as careful as we should be. Most virus problems can be cured with little data loss, provided they are attended to promptly. Having sensible email handling procedures and a decent anti-virus software package is sufficient protection for most people. But if your anti-virus software is not up to date, it is quite useless! And if you are still using Microsoft Outbreak, er Outlook as your email client after the Love Bug and Melissa and all those countless others, then you deserve what you get. We have no sympathy at all for Outlook victims. Ditto for people who get massive spyware infections because they insist on using Internet Explorer instead of any of the modern browsers (Mozilla, Opera, Firefox). |
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| Software Error |
While hardware gets more and more reliable every year, software only seems to get worse. (Actually, it's probably much the same as it was 20 years ago—it just seems worse.) Badly-written games cause quite a lot of damage to our fragile file-systems. Over-ambitious utility programs that claim to give you something for nothing are another common problem. (Double Space was one, but there have been many others.) And even "safe" office productivity software has its failures. Believe it or not, we still get calls from users who are about to loose a whole document because of the infamous "can't save" bug in Word for Windows.)
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| Hardware Failure |
The least common of the big four, but still a possibility you can never afford to ignore. Hard drive failure can happen without warning, and at any time in the life of the drive. The best drives fail less often, and may even fail gracefully so that you get some warning and can look to your backups, but they still fail. There is only one real rule of data safety: backup often! Since the advent of the CD burner, there has been no excuse for not backing up.
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