If you're thinking about getting into direct-to-disk recording or desktop video, then you'll also have to think about getting a whopping big hard drive. Ian Waugh finds that they don't come much bigger (or faster) than the Micropolis Microdisk AV hard disk

A hard drive is a hard drive, right? Unfortunately not. Like computers, there are many different hard drives, with different capacities and specs. When they first appeared, they cost as much as the computer they connected to, and it was unthinkable that anyone would ever need more than the 10Mb of storage capacity they offered.

How times change. The price of hard drives has plummeted, and continues to spiral downwards - and as for storage, most computer suppliers now recommend a minimum of 250Mb. It's not just to part you from a few extra Gregories - many of today's applications need large amounts of disk space, and 250Mb is a very sensible minimum size.

Normal applications - that is, those involving wordprocessing, spreadsheets and even MIDI sequencing - don't make heavy demands on a disk drive. The faster the drive, the quicker the program will load, but if you have to wait a few extra milliseconds while it sorts out an internal message, it's no big deal.

But for applications which require the transfer of data from a disk in real-time, such as direct-to-disk recording or video, any interruption in the data flow can result in glitches, causing the video or audio to stutter, skip frames or break up.

Standard hard drives are designed to transfer data in short bursts which leave short gaps in the data stream, so although data transfer may be fast it is not always continuous. You may have seen videos where this happens - even running a QuickTime or Video for Windows movie can be jerky, never mind trying to play a large-screen video or an eight-track digital audio recording. Advances in audio and video technology demand a new breed of hard drive.

Drive to succeed

Enter the Micropolis Microdisk AV drives. Micropolis has been manufacturing hard drives for donkey's years, and developed the AV series to provide a high, consistent data throughput. They do this in a number of ways. For the technically-minded they use fast SCSI 2 technology incorporating read-ahead, and write-behind caching. They minimise housekeeping functions which are liable to interrupt standard drives at any time, and they use a buffer to absorb any other delays which may occur. They also use advanced thermal calibration which ensures that the worst-case data access is only 30ms. A standard drive can take up to one second.

But specs can be misleading. Most drives quote a data transfer rate (DTR) but this is usually that which occurs during its peak activity. They may also quote a minimum DTR. A quick browse through a few hard disk ads showed that the minimum and maximum DTR for SCSI drives tend to range from 2.75-5.5Mb/sec. If you have an older drive or an IDE drive, you could expect the rates to be half that. However, few drives will quote a maximum uninterrupted DTR, as they aren't designed for that sort of operation.

The AV drives quote maximum and minimum DTRs of 4.3 and 3.0Mb/sec, with a maximum uninterrupted DTR of 2.9Mb/sec. They're not only fast, but their uninterrupted DTR is high. It's this factor more than the others which make the drives particularly suitable for audio and visual recording.

Other than that, the drives work just like any other. You'll probably notice an increase in speed if you use one alongside an existing drive. The AV on my machine ran almost three times faster than the IDE drive.

The AV drives have another trick up their sleeve - they're stackable. Anyone can buy several SCSI disk drives and plonk them on top of each other, but the AV drives have a modular design and use special subsystem cases, which enable you to build a mini hard drive tower holding up to nine disks.

The subsystems comprise various case parts, covers, SCSI connectors and so on, and you simply buy those you need according to the number of disks you want to stack. Most users may be happy with a single 1Gb drive, but Microdisks are designed for pro use and studios will welcome the ability to link several together.

Rugged individualists

Each drive in the system contains its own power supply and cooling fan (which is quite quiet). The front panel of each subsystem is easily removed and the drive itself can then be pulled out - it even has its own handle. This is another major plus for the heavier end of the industry, as it effectively makes the disks removable media. Not, of course, that you're likely to want to back up your data onto them, but it does make the data they contain easily transportable, say from one studio to another. It's far easier than backing up the data simply in order to move it to a new location.

Unlike most hard drives, the Microdisks come in a sort of DIY flatpack but they are easy enough to assemble. And they look rather better than an MFI wardrobe, too (What doesn't? - Ed). The SCSI connectors are at the back of the case, and if you are stacking more than one drive, you simply daisychain the connectors.

There are no adjustable controls or settings on the drive, just a couple of LEDs on the front to let you know it's on and it's busy doing its stuff.

Ready for the future

Finally, Micropolis backs the AV drives with a five-year warranty. Some other hard disk manufacturers do so too, but you'll still find many who only offer a one or two year guarantee.

The AV drives have already made a substantial impact in the A/V market, and companies such as Yamaha and Harman (distributors of Steinberg) are recommending them for use with their direct-to-disk systems. The drives are also ideally suited for use in networks, should there be any LAN managers reading this.

Because of the subsystem casing, the external drives seem relatively expensive, but the internal versions are particularly well-priced. In fact the RRP of the internal drives are on a par with other SCSI drives of similar capacity. As with any computer equipment, you can probably save a few quid if you shop around.

Do you need an AV drive? Well, with desktop video fast becoming one of computing's growth areas, it surely can't be long before games, home-based and multimedia applications are demanding AV performance, just as a CD ROM drive, SVGA and a fast 486 are now becoming the norm.

In any event, if you're serious about hard disk recording or want to get into desktop video, it just doesn't make sense to compromise the performance of your system. You could opt for a fast standard drive, but it wouldn't be optimised for A/V use, and that's the important thing to remember. The review drive performed faultlessly, and I have no hesitation in recommending the AV drives, particularly to anyone involved in hard disk recording or video editing.

The essentials...

Price inc VAT: 1Gb internal £705 (£1110.50 inc subsystem), 1.7Gb internal £1010.50 (£1400 inc sub system)

More from: Micropolis Ltd, (Contact Details)