The Case of the Missing Capacity

A group is complaining that computer vendors misstate the capacity of drives shipping in their boxes. You don't have to be Perry Mason to see that the figures don't add up. But what do customers really want to know about useable storage capacity?

About a dozen years ago, a class-action suit was filed to force computer makers and display manufacturers more accurately to describe the viewing area of their screens. And now, according to a news report late last week, a similar suit aims to straighten out the way vendors describe the capacity hard drives found in computers.

According to Reuters, a group of consumers last week filed a lawsuit against a number of computer makers, including Dell Inc., Hewlett-Packard Co., Sony Corp. and even Apple Computer Inc. The lawsuit alleges that computer companies engage in deceptive marketing practices when a hard disk is described as comprising 20GB but actually offers a lower readable capacity. The plaintiffs called for "restitution and disgorgement of ill-gotten profits," among other demands.

This new suit over storage resembles the class-action lawsuit brought against CRT monitor and computer vendors in the mid-1990s, People v. Acer Peripherals, Inc., et al., which was settled in 1997. Before that time, vendors took the measurement of the bare tube before it was wrapped in the enclosure. Naturally, the housing reduced the actual viewable area. Today, display vendors give both the gross measure and the viewable area. For example, a 21-inch monitor will have a viewable measure of 20.18 inches.

The storage complaint, which is seeking class-action status, points to the differences between the usually stated size of a disk and its formatted capacity because of the differences between decimal and binary expressions of storage capacity.

Decimal numbers are powers of 10, while the numbering used for digital products is binary, or based on powers of two. This difference can bring a tax of about 7.5 percent for storage capacities in the tens and hundreds of gigabytes. So a 30GB drive will provide a formatted capacity of about 27.94GB. The so-called "missing" capacity is because of the binary-decimal difference as well as the allocation tables and other formatting overhead.

A proposed standard covering this difference has been crawling for years through the various technical committees and the International System of Units organization, a k a SI. (These are the people who brought us the metric system.) The standard is IEEE 1541 Units and Prefixes for Digital Electronics.

Since this situation has existed since the beginning of the personal computer industry, its difficult to see that theres really any confusion anymore, even among consumers. Technically savvy owners understand the issue, and most consumers dont understand capacity. This is a different situation than we had with monitors, since users cant check their capacity with a measuring tape.

Besides, most computer vendors put a disclaimer in their brochures. Something like, "1GB means one billion bytes when referring to Hard Drive capacity; accessible capacity may vary." Or even: "actual formatted capacity less." This must mitigate some of the alleged deceptive marketing.

However, computer manufacturers could do better and provide some useful information—even for those of us who understand storage. Computers today come with a bunch of programs and files pre-installed. Wouldnt it be better to know at purchase time approximately what storage capacity will be available for the files and apps that we will add to the machine?

Buyers should have some idea about the capacity left over after formatting 2GB for Windows XP and the 250MB common installation of Office XP Pro. And if the machine comes set up with a recovery partition, maybe that should be folded into the calculation, as well. (Sony, for one, mentions this latter spec in its technical specs.) Storage Editor David Morgenstern is a longtime reporter of the storage industry as well as a veteran of the dotcom boom in the storage-rich fields of professional content creation and digital video.

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