We are at a major turning point in PC mass storage development. Removable storage is pretty much the only thing that has remained the same in the last 10 years. Now, however, the market is fragmenting, the ubiquitous CD-ROM is about to be superseded, and storage capacities continue to grow at a frightening rate. Some breakthroughs will impact corporate purchasing this year, while longer-term developments should make the magnetic disk as obsolete as paper tape.
In the early days of PCs, removable storage meant 5.25in floppies. These low-capacity disks were worryingly fragile: hardly the ideal storage medium. IBM's PS/2 range, launched in 1987, changed everything.
It was intended to wrest back control of the PC.
Looking at a PS/2 now, we see an uninspiring, low-spec machine, but it's hard to remember the revolution it represented. The ill-fated Microchannel bus, shiny new VGA graphics and the 3.5in diskette made this a powerful new contender that ran the old software, but was hardware incompatible.
The ploy didn't work. PS/2s didn't leave the rest of the world behind, but the immense superiority of the new diskettes rapidly doomed the older format.
In a business where machines move from leading edge to entry level in two years, it's amazing that the 1.44Mb disk has stayed with us this long. Of course there are legitimate challengers. Syquest and Iomega both have excellent devices around the 100Mb-200Mb mark, and more recently around 1Gb. These are popular for backup and extending hard disk capacity, but they aren't true diskette replacements.
There are a couple of reasons for this. One is backward compatibility. Although the industry managed the move from 5.25in to 3.5in, it was not painless. For a while it was common to have dual format machines - a painful waste of money - and much time and effort was spent transferring data between formats.
Iomega's Zip drive and the Syquest EZFlyer may be extremely effective, but they're totally incompatible with diskettes. The second problem is transparency. Diskette drives are recognised by DOS and have controllers built into every PC. The newcomers are rarely supported so directly.
Now it seems the 1.44Mb disk has a natural successor - the LS120, developed by 3M spin-off Imation. Compaq has been quietly using 120Mb drives in high-end machines for a while, but 1997 is the year when they will break into the wider market. LS120 drives benefit hugely from being able to read existing disks. After all, there are reckoned to be 3.5 billion of them out there. It has been possible to store much more on a diskette for a long time, but not to find the data. LS120 uses a laser to locate the tracks, allowing an increase from 135 to 2,490 tracks per disk.
The LS120 brings not only increased capacity, but speed. Almost as impressive as the five-fold increase in read/write speed on LS120 disks is the ability to read conventional media three times faster and write them five times faster. The disks themselves currently cost around 20 times the price of a 1.44Mb diskette, but prices can be expected to fall quickly as they move into the mass-market. Similarly, the $100 premium an LS120 drive adds to a machine, will soon drop.
Corporate purchasers should be talking to their vendors about LS120 - and if they can't be delivered this year, it's a good reason for considering an alternative supplier. Bear in mind, however, that DVD-RAM, the rewriteable form of the next generation CDs' could be the standard for removable storage within five years, so the LS120 may prove to be a transitional solution.
While there's no immediate breakthrough in the hard disk arena, technology continues to improve, pushing more capacity into a small space at ever decreasing cost. An entry level PC with less than 1Gb of storage is a joke now. IBM has just brought out a 5Gb drive for laptops, and there is more to come. The once flourishing market in disk compression has quietly sunk into obscurity - it's so cheap to add a couple of gigabytes of hard disk that it's rarely worth the effort to compress.
This trend will continue for some time, but there is a limit.
Laser-read storage, typified by the CD-ROM, has made a huge difference to software publishing. This year sees two remarkable changes. Firstly, the DVD (variously described as Digital Video Disk and Digital Versatile Disk) is set to push the CD-ROM into obscurity. Secondly, this publishing medium will rapidly become storage as well.
As with CD-ROM, DVD began in the entertainment industry. The CD might have been enough to render black vinyl a museum piece, but it hasn't enough capacity for digital video. You can't get a whole feature film on a CD, and the thought of changing disk part way through a movie is the kiss of death for this otherwise convenient medium. UK's Nimbus has been demonstrating higher format CDs for a while, using a blue laser to cram more in, but DVD is the true successor.
Unlike CD, DVDs will come in a number of formats. Once the dust settles, though (and it's expected to be a quick process), players should cope with any format, and there's the promise of a minimum capacity of seven times that of a CD, plus backward compatibility with CDs too. Add to this an equivalent of a 9x CD-ROM speed for starters, and you've got an impressive bundle.
DVD uses a number of tricks to cram in the extra capacity. The first is the oldest in the book; like floppies, DVDs can be double sided. Unfortunately, as with the early floppy drives, it will, initially, be necessary to flip the disk in the reader. But it seems unlikely that companies who can fit a six disk autochanger into a standard slot will be defeated by the possibility of reading both sides of a disk. Next, DVD uses a red laser instead of the traditional infra-red, which allows the data storage pits to be made smaller and crammed into tighter spirals. Finally, there are double layers. CDs have a reflective foil below the pits to reflect the laser. A dual layer DVD has a semi-reflective layer with a second set of pits under it, then a fully reflective layer.
While CDs themselves have not changed in capacity, there have been developments. CD writers have gone from being bulky, hugely expensive devices, to drives that fit in a conventional bay and cost only a few hundred pounds. Writing CDs is not a universal panacea, though. Apart from being irreversible, the limitations of the format make it more complex than popping information onto a disk. CD-Erasable, the multi-write version of the recently released CD-RW, will soon overcome these problems.
CDs can be reused, making them a true storage medium. Unfortunately, though, CD-Erasable is likely to be rapidly overtaken by the read/write DVD-RAM, and should only be used if timescales require it.
There is, of course, another class of rewriteable laser disk represented by the assorted magneto-optical solutions. These are fine, but suffer from a lack of compatibility with CD-ROM (apart from the slightly clumsy dual-format drives) and each other, and will inevitably be sidelined by DVD-RAM.
Within a year, corporate buyers should expect machines to be fitted with DVD as a matter of course - and within two years, DVD-RAM. A write-once version, DVD-R will also be available for those who need it. John Taylor, program manager for special projects at IBM has no axe to grind over DVD, but he is clear about the future dominance of DVD-RAM. "I expect the price of DVD-RAM (hardware) to be within $50 of DVD by next year - DVD-RAM will be the primary removable storage medium by around 2000," he says.
Although there has been unprecedented movement in mass storage of late, there is much more to come. For example, in the removable market, Imation and TeraStor are intending to deliver 20Gb drives with performance comparable to hard disks in 1998. Using a combination of hard disk and optical technologies, the Near Field Recording approach of this medium is highly impressive. However, current technology can only be pushed so far.
IBM is already investigating the alternatives. As Taylor points out, "there are two fundamental limits to the hard disk. There's only so far we can lower head flying heights and we're running out of molecular space.
Also, there comes a point where the magnetic domains that hold the information become too small." Probably the best bet at the moment is holographic storage.
The Star Trek-like concept of massive storage on solid state crystals is very attractive. But researchers are trying many other means to pack more and more data into less and less space. Even more remarkable than holography, is the possibility of using protein molecules to store information.
Some proteins, notably bacteriorhodopsin, undergo structural changes when exposed to different coloured lights. Although there are several states the molecule passes through, at least two are stable enough to represent a bit. The WM Keck Center for Molecular Electronics estimates data can be stored for around five years in this manner. As the states absorb light differently, it is possible to read the biological data using a laser. Protein storage research is less advanced than holographic, and will not achieve the same transfer rates, but has the potential to cram even more storage into any given space.
Whatever the medium, it's a safe bet that storage will continue to drop in cost and will make the huge information needs of the next millennium increasingly practical.
CD-RW: how it works
CD-ReWritable is essentially a CD-Recordable (CD-R) with the additional benefit of a rewrite function. Based on phase-change technology, CD-RW allows discs to be rewritten many times over.
The CD starts with a polycrystalline recording layer made from silver, indium, antimony and tellurium. During recording, a laser selectively heats areas of the recording track melting the crystals which are then rapidly cooled to an amorphous phase.
The relative difference between the way the amorphous and crystalline areas of the disk reflect light can be used to store data as binary ones and zeros. When data is overwritten, amorphous areas are heated to return to the crystalline phase.
Crystal cages: information set in stone
Although mass storage capacity continues to increase in leaps and bounds, the limits of magnetic technology are in sight. Before long we are likely to need a radically new approach. Holograms offer an exciting possibility.
If the mechanics of holographic storage can be made commercial, it would be possible to reach transfer rates well above 100Mb per second, as there is no need for any moving parts. It would be quite feasible to store 2Tb in the volume of a typical half-height disk drive with minimal risk of failure. Another remarkable aspect of holographic storage is that physical damage to the holographic crystal will not necessarily result in loss of data. The image becomes dimmer, but the entire data is held in each piece of the hologram.
Holographic storage isn't easy. The data to be stored is displayed as an array of dots on an LCD, which is then effectively photographed and combined with a reference laser to produce an interference pattern. Great accuracy is required in the laser angles and the quality of the photosensitive material used to recapture the data. IBM, leading the research into this field, reckons holographic storage will be commercially viable on the desktop in the early years of the next millennium.
Desktop storage: the next generation
As desktop storage moves into the next generation, we've a whole new set of prefixes to learn. Overlooking arguments about 1,000 vs 1,024, here's the PC Week crash course:
Unlike its predecessor, CD-ROM, DVD is not a single standard.
A DVD disk can come in a range of flavours:
And it doesn't stop there, with DVD-R write-once and other DVD-RAM formats, each having their own capacity variances, expected too.
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