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Removable storage

Copyright Daniel Rutter 1996. All rights reserved.

 

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You need more space. You need it now. You’ve got as many hard drives as you want. What do you do?

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Data expands to fill all available space. It’s true - and never more true than in multimedia applications, where gigantic data files and extensive backup libraries that need to be readily accessible are the rule, not the exception.

If you’re after quick access to tons of data without spending a fortune, you need a removable cartridge drive or a CD writer. The first gives you speed, simplicity and erasability, the second gives you dirt cheap universally legible media. We checked out the major offerings in each department, and the issues you should be aware of.

 

The big brawl - SyQuest versus Iomega

The single big name in mass market removable storage used to be SyQuest. SyQuest drives are not particularly revolutionary in concept - the cartridges use ordinary rigid hard disk platters - but they have the advantage of speed and ubiquity. SyQuests have and have always had hard disk performance, and everybody uses them.

SyQuest Technology, though, is not doing well. Over the four quarters ending 30/6/96, SyQuest has lost $US145.3 million, with modest profits in the two quarters previous. Another company’s fortunes have been quite the opposite; $US36.1 million in profits over the last four audited quarters and small losses in the two before.

That company is Iomega, makers of the wildly popular Zip and faster, bigger Jaz.

Iomega could have been broke by now, if SyQuest had bought the Zip technology from Fuji when, according to some reports, it was offered to them. But they didn’t, and they ended up feeling like Decca Records when they rejected the Beatles ("…guitar music is on the way out"). SyQuest’s executive vice president for sales and marketing, Chet Brown, has been quoted as describing the decision as "a major screwup".

Nobody anticipated the Zip drive’s popularity - not SyQuest, and not Iomega either.

In the years BZ (Before Zip), removable storage was deadly boring, because it was fairly complex and rather expensive. Quite a few ordinary computer users bought SyQuest drives for backup and archiving, but the major market was professionals.

In 1995, Iomega sold something close to a million Zip drives. Slower and smaller than the then-current generation of SyQuests they were, but they were also notably cheaper, tougher and cuter. Iomega was overwhelmed by demand and had considerable difficulty filling orders - Zips are now made on contract by Seiko-Epson, and marketed with Iomega, Epson and Reveal branding, though all sales are credited to Iomega. All Australian Zips are presently Iomega branded, but the product’s exactly the same behind the badge.

When Zips were selling like hot cakes, SyQuest panicked. They came up with the EZ135, a rushed-to-market single-sided version of the 270Mb 3.5" drive that was no more robust than its full-capacity cousin, wasn’t anything like as cute as the Zip and was sold at a price so low that SyQuest lost money on every sale. This attempt to buy market share fell flat, and the development time of the EZ135, which didn’t advance any technologies, put SyQuest behind in the innovation race.

Now SyQuest are trying to get their act together. They’ve shifted to an all-new manufacturing plant in Malaysia, more than half of their employees have been shown the door, management has been purged and restocked and two new products are out.

For the low end, there’s the EZFlyer 230, which lines up against the Zip. People needing more capacity are served by SyQuest with the EZFlyer, which competes with Iomega’s Jaz. Both products have come out after their competition, so SyQuest’s playing catch-up in more ways than one. Whether they’ll succeed is unclear. The purpose of a comparative review like this is to tell you whether they deserve to.

 

Big, fast, cheap - Jaz versus SyJet

Iomega’s Jaz drive is not The New Zip. That’ll arrive some time in 1997, when the 200Mb version of everyone’s favourite purple drive comes along. The Jaz is aimed at users who need a lot more space, can sacrifice a bit of toughness to get it and would also like notably better speed than the Zip’s languid seek and transfer specs can deliver. But it’s not without competition.

SyQuest’s latest product is the SyJet, a 1.3 gigabyte drive that beats the Jaz significantly in capacity and price. The capacity advantage is about 20%, not the 30% the SyJet’s name might appear to suggest, because the Jaz’s formatted capacity is 1020 real megabytes and the SyJet is 1.3 unformatted hard drive manufacturer’s megabytes (see "Megabytes Ain’t Megabytes"), but the SyQuest still has a significant dollars per megabyte advantage. Unfortunately, more than a month after the drive’s official release in Australia none were available for review, and so we have no first-hand experience with the SyJet.

The Jaz outspeeds SyQuest’s old flagship 270Mb drive by 30-50% overall, and quoted speed specifications put it faster than the SyJet, though not by enough to make a difference. Super-speed is not dreadfully important for most users. While the Jaz and SyJet are both fast enough for better-than-VHS digital video, they’re not really big enough for serious use. The Jaz can manage sustained write rates of better than 3Mb per second and reads close to 5Mb/s, on a fast machine with an appropriately speedy SCSI controller. If you actually use all of that speed, you’ll be able to fit little more than five minutes of video onto a cart.

Third party array systems are available for the Jaz which let you use two or more drives in a striped configuration (byte 1 goes to drive 1, byte 2 to drive 2 and so on, wrapping around at the last drive), they’re eminently suitable for serious video and power DTP applications, but the vast bulk of users will have just the one drive. Nonetheless, Iomega aren’t ignorant of the multi-drive market sector; the external Jaz case is stackable.

The Jaz has proper SCSI ID selection (against the Zip’s address 5 or 6 switch) and a pair of the new style HD-50 high density SCSI connectors on the back. Like the Zip, it’s got built in termination; unlike the Zip, the termination can be automatic. The Jaz cannot be stood on its side, like the Zip, but it has a power switch, unlike the Zip.

The basic designs of Jaz and SyJet are similar - they both use cartridges containing two traditional rigid platters. Hard drives have been multi-platter for ages, because it greatly reduced the required data density and boosts reliability. The Jaz is a more elegant execution of the concept, though; its cartridge is better designed, with a rattle-stopping platter clamp system and better dust exclusion and management. Some Jaz cartridges cause a noticeable vibration of the drive when up to speed, but this is the only noticeable hardware flaw.

A major advantage of both the Zip and Jaz is look and feel. A big part of the reason for the Zip’s acceptance in the home market was its From the Desk of Jean-Luc Picard appearance, and the Jaz carries on the family lineage with a slightly longer but similarly styled green case. The SyJet is styled very similarly to the EZFlyer - the only obvious change is the top window, which is oval instead of rectangular.

Like the Zip, the Jaz comes with PC and Mac software that aims to make setting the drive up for basic operation and cartridge management easy. Unfortunately, while Iomega’s hardware designers should be put on a pedestal and applauded, Iomega’s software guys should be used to bulk out the concrete from which the pedestal is cast.

Some of the Jaz software may work OK for you. One test machine we used had more than 16Mb of RAM and an ISA bus mastering SCSI controller. The Jaz support software didn’t like this, and refused to write enable the cartridge. To overcome this problem, you have to install DOS drivers for your SCSI card and do a two hour format with surface check. I was not that dedicated, and just formatted the cart on the 8Mb server instead.

This is not the only aspect of the Jaz software that needs work. The utility included to allow you to configure or disable the drive’s sleep mode, which spins down the cartridge after 30 minutes of inactivity, does not work. At all. Most systems send the right SCSI command to wake the drive up again. Some don’t. If yours doesn’t, you’ll have to eject the cartridge and insert it again until a working version of the utility comes along. Amiga users can use SCSIMounter to wake up the drive, or pop and reinsert the cart.

Note that the Jaz software problems are not important. You do not need the software to use the drive. It’s a SCSI device, so all you have to do is set the address and plug it in. But if you want cartridge password protection, software write protection and nifty right-click menu options for easy management of Jaz and Zip carts, go ahead and install it. Just remember, after the software’s installed, to zap the 875Mb of crud on the Jaz Tools cart supplied with the drive. Some of this is software for various platforms, the rest is useless animations of the drive, the Iomega logo, and some guy playing a saxophone and conducting a conversation with a Jaz.

The Jaz wins on look and feel. It’s effectively even on performance, unless you buy more than one and an array system. It’s a little behind on price - Jaz drives are cheaper than SyJets, but the carts are significantly more expensive per megabyte. It will probably win on durability, based on design, past performance and reports so far. No real-world reliability information is yet available for the SyJet and what’s available for the Jaz is only anecdotal, but it’s reasonable from the evidence available to assume Jaz cartridges will survive more disrespect than SyJet carts. Jaz would definitely win on bundled software, if it worked, since this is one area where the SyQuest copying crew has barely started work. As it stands, the bundled Jaz software is more trouble than it’s worth.

Both the SyJet and the Jaz are incompatible with previous technologies - the SyJet may be 3.5", but it can’t read any other SyQuest format, and the Jaz can’t read anything but its own cartridges either. This means SyQuest loses one of its prime advantages - the ubiquity of its drives - when it’s trying to sell the new model.

Without real world data on the SyJet or the chance to review one, we can’t recommend either drive with certainty. But if you need a 1Gb removable drive NOW and want to play the odds, Jaz is the way to go.

 

The cheap seats - Zip versus EZFlyer

Everybody loves the Zip. It’s less than $300 ($349 list, with a $50 rebate deal until the end of the year), it’s robust, it’s tolerably fast, and it’s even available in an internal version now - though these are hard to find, since they’re really aimed at computer makers like Power Computing, whose Mac clones come with Zips as standard.

The Zip technology hybridises conventional magnetic heads, as seen in SyQuests, and flexible disks, as seen in Iomega’s older Bernoulli drives. The result is not as robust as the Bernoulli, but both drive and media are still highly tolerant of abuse.

The Zip’s shortcomings are few. No power switch. SCSI addresses 5 or 6 only (a slower but more transportable parallel version is also available). You can stand it on its side, but it then falls over under the weight of its cables unless it’s propped or wedged.

But it’s simple, it’s cheap, and it is now very widely accepted. If you need a removable drive for moving chunks of data not larger than 97Mb, Zip is the cheapest and close to the toughest way to go.

SyQuest’s EZFlyer is a much newer product. It’s not much larger, physically, than the Zip, but its single platter cartridges have much higher capacity - 225Mb before formatting. It’s much faster than the Zip - slower than the old SQ270, but not by much.

The EZFlyer shamelessly apes the Zip in styling. Similar colour, same viewing window in the top, same rubber feet on the side. It also finally deals with one of the long-standing annoyances of SyQuest drives - it’s got a proper cartridge eject system. Every other SyQuest from the old 44 to the 270 has had a button you press to initiate the spindown process and a lever to actually eject the cart when, and only when, spindown is over. This inelegant and slightly dangerous arrangement should have gone the way of the dodo long ago, but better late than never. The good old SyQuest manual eject hole’s still there, for when you need the cart out but you can’t plug the drive in - now you stick your unbent paper clip in a hole on the bottom instead of the front.

The EZFlyer also has three other features the Zip doesn’t - a power switch (luxury!), proper SCSI ID selection in the SCSI version, and a dust exclusion door on the front. The Zip seems to have absolutely no need for a dust exclusion door. But no matter.

The EZFlyer has more than twice the capacity of the current Zip and is about twice as fast, in normal use, for the SCSI versions of each drive. Neither is really fast or big enough for video or other demanding applications, but if you’re flogging carts all day you’ll appreciate the SyQuest’s greater speed and capacity.

Is it, though, a good buy?

It is a generally accepted convention in the computer journalism business that hardware sent to you for review will be top quality. It makes sense for companies to make sure that, if they make any lemons, they don’t send them out to reviewers. You might not have time for Rolls-Royce quality control on every product, but the review models should be flawless.

So it’s rather disturbing that the last two devices we’ve received for review from SyQuest have been dead on arrival. The EZ135 we got for review months ago was completely deceased - it wouldn’t even start to spin up a cartridge, and had to be ejected with a paper clip if you inserted one. And the first EZFlyer we got would spin up its included cart - but then it spun it right back down again and spat it out.

There can be no excuse for this. If you send drives like this to the press, what the heck are you selling to the public?

The second EZFlyer worked. We haven’t had time to run it for a few months and see if it suddenly starts killing cartridges, as some 270s and EZ135s did; the EZFlyer has lower data density (or more error correction code on disk) and somewhat better dust exclusion, so it should be more reliable than its predecessors. Perhaps SyQuest have got it right this time. But the inescapable fact is that they got it wrong before.

 

MO Monsters

The Sony RMO-S594 and Maxoptix OptiStor T4-2600 are magneto-optical drives whose "2.6 gigabyte" cartridges offer about 1.2 gigabytes of formatted storage per side. The drives do not automatically read both sides of the cartridge - you have to flip the cart over. You can also use older 1.3Gb and 650Mb carts, which similarly have their total capacity shared between the two sides.

Apparently, some Macintoshes have problems with the standard one kilobyte per sector carts and have to use 512 byte per sector media, which because of higher formatting overhead have 88% of the capacity of 1024 byte per sector disks. Both types of media work fine on machines capable of using 1k/sector disks.

The OptiStor is not a particularly fast drive - its sustained transfer rate is a bit more than 2Mb per second and its 35mS-plus seek speed is on a par with the cheapo Zip drive. You’re unlikely to notice the sluggish seeking, though, because the T4 uses its 1Mb of cache RAM intelligently. The cache means the drive may well be chugging away for a while after the computer reports an operation complete, but this is only significant if the drive’s turned off before it’s really finished. You can disable the write cache to reduce the chance of accidental data loss, but this will only really protect you from your own absent-mindedness; write operations will still take much the same amount of time, and a power failure during that time will cause problems, cache or no cache.

The Sony drive has a 4Mb buffer, and its seek speed is considerably better, at around 25ms. You pay more than $1600 more for these extras, but they do make a noticeable difference. The drive is still unsuitable as a scratch device - you don’t want to run applications from it, and it’s a really lousy place to put a swap file - but gigantic data files and intensive seek operations are something like 50% faster overall than on the Maxoptix.

In the durability stakes, magneto-optical always scores well. The T4 drive itself is built like a tank, and the external model tested came in a plain Jane steel case that made this drive easily the heaviest in the comparison, and the only one you could safely stand on. Don’t know why you’d want to, but you could. Media durability should also be very good

On the downside, the case also makes the T4 the loudest drive in the comparison - its hefty cooling fan was louder than the three-fan computer it was sitting on. I’m not personally bothered about noisy fans, but I understand that more houseproud users find them irritating. Going for an internal drive instead will solve this problem, if you’ve got a spare 5.25" bay.

The Sony drive is slightly less robust but more elegantly constructed, with a much quieter fan. That extra cash does buy you some more refinement.

Bear in mind that an ironclad case does not make a drive invincible. Knock a drive in a chunky case off a desk and the case, power supply and fittings may be A-OK - but the drive itself may be hopelessly out of alignment or otherwise damaged, especially if it had a cart inserted when it fell. Then again, heavier drives are harder to knock in the first place.

In use, both drives felt quite acceptably speedy with write verify and write caching turned on. Long sustained transfers and hard thrashing of fragmented carts betray the speed of the hardware under the cache, but for everyday file operations there’s no problem. The bigger the file you transfer, the more you see the true speed of the drive, but a 10Mb file will transfer to the Sony in under 10 seconds even with a budget SCSI controller, if you’re using a Windows 95 machine with a decent amount of RAM. The Maxoptix is not much slower. The drives may be pricey - particularly the Sony - but the carts are cheap. If you need a ton of rewritable storage, the Optistor, Sony or another 2.6Gb magneto-optical will provide the most megabytes per dollar. If you can afford to wait, though, faster units with 4.6Gb capacity should be locally available Real Soon Now.

 

PD Drive

The Panasonic PD Drive (the version we tested was NEC badged; you can get them with various names on the front panel) is an oddity in the removable storage world. It works as a 650Mb removable drive, and as a regular CD-ROM drive as well. It’s a rare computer these days that doesn’t have a CD-ROM drive anyway, and probably faster than the PD’s quad speed performance, but if you’re not oversupplied with internal 5.25" drive bays then being able to amalgamate the two devices helps. Thankfully, you don’t need any special adaptors or caddies; the PD drive’s tray can accept a CD or a PD cartridge.

The PD drive’s cartridges format to about 632Mb, which puts it in between the cheap mass market drives and the big boys. It’s a long way from SyJet or Jaz speed, though.

The seek speed of the PD drive is 150ms or so, which is impressive for a CD-ROM drive but not for a rewritable device. The transfer rate is also CD-ish - the quoted speed is less than 1.2Mb/s, which puts the PD drive with a cartridge in line with current oct speed CD-ROM drives. The worst write speeds we managed to get from the PD drive on a Windows 95 system were around 250 kilobytes per second, and on sustained transfers it never managed a write speed better than about 300k/s. This is half the performance of the parallel port SyQuest EZFlyer, let alone the SCSI one. Read speeds were a lot better, at about 900k/s; the limitations of the parallel port make the parallel EZFlyer slower to read than to write, and it was almost half the speed of the PD Drive for this test. The degree of caching provided by the drive and the operating system meant transfers of single smaller files were more than acceptably fast. Overall, in operation, the PD Drive feels like a big Zip. Unfortunately, many removable drives have large files pumped onto them all the time; if you’re copying a 200Mb file onto a PD Drive, you’ll have time for a cuppa.

The PD drive’s dual purpose nature and low price makes it a natural for inclusion in CD-equipped laptops and a good idea for budget-conscious users who don’t need to buy what everyone else has. At present, its lousy speed hobbles it somewhat, but the technology is young. Faster versions, possibly with higher capacity, are likely.

 

 

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Why smaller?

Many removable cartridge drives are compatible with cart capacities smaller than their maximum. The usual reason for this is to maintain backwards compatibility with older versions - that’s why, for example, a 200Mb 5.25" SyQuest drive works with the old 88 and 44Mb carts.

But what about drives like the SyJet and Zip, which on release have a full sized cart (1.3Gb and 100Mb, respectively) and an undersized version (650Mb and 30Mb, respectively), which did not previously exist? Practically nobody actually uses the smaller carts, which are more expensive per megabyte than the full sized ones - what’s the deal?

Use of defective media, that’s what the deal is. When you’re making hard drives or removable cartridges, you test each platter or cart when it’s made. If it passes, you stick the standard full capacity sticker on it and send it out. If it fails badly, you chuck it away. If it’s not up to scratch for full capacity but also isn’t bad enough to be junked, you give it a lower capacity sticker and an appropriately modified case and/or support firmware, and with any luck manage to make some money on what would otherwise be a dead loss.

It is important to note that this sort of thing is perfectly normal in the computer industry, and nothing to be concerned about. Many performance-critical computer components, especially hard drives and CPUs, are performance tested on the production line and assigned a rating that conservatively estimates how much data they can safely hold or how fast they can be clocked. 50MHz 486s would have been 60MHz if they’re passed the test; the same applies to 90MHz and 100MHz Pentiums. Super-performance componentry like this doesn’t get a simple pass/fail mark from quality control.

Nonetheless, drive and CPU manufacturers are not eager to promote this aspect of the production process, because in the eyes of the uneducated it looks as if second-class components are being foisted on the public. If components failed the high capacity test but were sold as high capacity anyway, this would be the case. But they aren’t. Do not be alarmed.

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Other technologies

Bernoulli - the old trouper

Iomega’s famous today for their stylish Zip and Jaz drives, but they’ve got a removable storage pedigree almost as long as SyQuest’s. Iomega goes back to 1983, when a 10Mb eight inch drive was pretty impressive and "Sy’s Quest", as recently-resigned Syed Iftikar’s company then was, was still making a custom drive for the military. Iomega’s old flagship product, the Bernoulli drive, is still in production. It topped out at 230Mb capacity a couple of years ago, and looks unlikely to be developed any further.

Bernoulli drives are big chunky 5.25" units - they show their age, against teeny 3.5" SyQuest and magneto-optical carts with the same capacity. But they were and are the toughest removable cartridge drives money can buy.

Realistically, few users need the degree of resilience Bernoullis deliver, but for odd applications like data logging in harsh environments and archival storage of fantastically important information, Bernoulli is the way to go. The drive can deliver uninterrupted data while being shaken hard enough to destroy a powered down SyQuest, and if you actually jar it enough to interrupt the data flow the rotation speed of the flexible disk drops and the surface falls away from the heads, making it practically impossible for physical head crashes to occur. Speed is better than the fastest of today’s magneto-opticals, but not up to modern SyQuest benchmarks.

Bernoullis aren’t very well known in Australia - they’re more popular in the States - so they’re not much use for tasks like moving files to output bureaux. And cartridges are relatively expensive. But if you need a remarkably tough external drive, a Bernoulli could be a wise purchase. Second hand units are very unlikely to be defective.

 

Floptical

With optical servo tracks to help a conventional magnetic head locate itself on the disc and the ability to read and write conventional floppy disks, the old 21Mb floptical drive was, well, a flop. It was an embarrassment to Iomega, the leader along with now-defunct Insite Peripherals of the consortium that made it. It was glacially slow, not especially cheap, and discontinued in early 1994. Sporadic reports of larger capacity versions have come to nothing. Around 70,000 flopticals were sold in the product’s two year life; Zips are selling something like 40 times as well.

 

MiniDisc Data

Sony’s MiniDisc has found a home in professional and semi-professional audio, when people want near-DAT quality with random access, but that’s where it’s stopped. The 140Mb MiniDisc Data drive was never officially released in Australia, after an overseas reception cool enough for use in superconductivity experiments. Too slow, too expensive. Sharp are promising a 700Mb version in the near future, which may or may not sell. Cute little 2.5 inch disks, though.

 

WORM

Write Once Read Many is a technology functionally equivalent to CD-R - you can only write a single time to the cartridges. Models are available with up to 1.4Gb capacity, but cheap CD burners with their media-anyone-can-read have eaten their market. WORM carts are tougher than CD-R, with a quoted shelf life of 100 years; if you’re making a time capsule, they could be a good idea.

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What about tape?

In the olden days, tape drives were the only option for large capacity data backup. They’re still very popular, because the media are cheap and reliable, and commonly available in enormous capacities - the popular DAT data drives get 4Gb onto a tape before compression, and the popular 8mm Video 8 format data drives fit 2 to 5Gb per tape, with data transfer rates of a few hundred kilobytes per second. But tape drives are useful for only one, tightly defined application - regular backups with infrequent restores. Even if you use an ultra-friendly tape handling system that makes the tape look to the operating system like a normal random access device, it still has to spend minutes spooling back and forth to find files. You can’t just grab the tape off the shelf, pop it in, grab your file and keep working; there’s often time for a coffee break.

But tape is cheap and reliable and well accepted. If all you need is backups which you anticipate restoring only in the event of a disaster, it’s fine.

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Removable drive applications

There are lots of things you can use a high capacity removable cartridge drive or CD writer for.

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Megabytes ain’t megabytes

Hard disk and removable drive manufacturers have a special sort of megabyte. As far as most of the universe is concerned, a megabyte is 1048576 bytes - 1024 kilobytes, each of which is 1024 bytes. But as far as drive manufacturers are concerned, a megabyte is one million bytes - and a gigabyte is one American billion, a thousand million. RAM manufacturers can’t get away with this because their product follows the binary rules that make computers work in powers of two, but disk storage can be made to any capacity and the capacity is traditionally a nice round number.

This means a "one gigabyte" hard drive or cartridge will have a capacity of 1,000,000,000 bytes, 7% less than the number of bytes you in a genuine gigabyte.

And this isn’t the end of it. The quoted capacity is unformatted - it’s the area of the parking lot before you paint the lines on it. The actual formatted capacity depends on the operating system you’re using and the type of disk you’re formatting, but it will always be a few per cent less again.

Keep the inflated size statistics in mind if you’re shopping for removable - or fixed - storage. The only manufacturer that’s broken this rule is Iomega, whose 1Gb Jaz cartridges really and truly ARE very nearly one whole honest to goodness gigabyte - 1020Mb PC formatted capacity, to be exact. Inflated numbers are still fine for comparison purposes, but if your application needs all of the quoted capacity of a given cartridge, not 91% of it, be wary.

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Reliability

Will the shiny new removable drive you just bought to store your information for years and years actually do the job? Probably. Can you be certain of this? No.

Rewritable disk cartridge drives and CD writers are both capable of being used for very reliable long term data storage, but mishaps and manufacturing defects can and do cause disasters. Just about all problems can be avoided with a simple backup strategy, but backing up is like exercising and eating well - everybody acknowledges it’s important, but far fewer actually do it, and even stringent backup policies won’t save you from losing as much work as you’d done between the last backup and the disaster.

Hard data on the relative reliability of different storage methods is difficult to come by, because manufacturers do not have time machines. If they did, they could fill a thousand cartridges with data, go back to the year 1796, bury the cartridges in an out-of-the-way-place, then dig them up today and see how many still worked.

In our depressingly Einsteinian universe, however, reliability testing involves taking those thousand cartridges and using them until, say, 10 fail, and then saying that that period of time multiplied by 100 is how long you can expect between failures of an individual cart. This does not take into account ageing; it’s an expression of the chance of failure of a near-new cart, and this is how MTBF (Mean Time Between Failures) figures are generated. They are less useful than many people think; a device built with a bomb in it that blew up after 1001 hours of operation could have a MTBF of 250,000 hours, if the evaluation units were only tested for 1000 hours.

Given the uncertainty involved in manufacturer’s figures, you have to go with known data. It is known that Zip cartridges, like floppies, are very durable. But they’re too small and slow for many applications. All magneto-optical and phase change media are inherently immune to magnetic data destruction. But magnetic corruption, in the real world, is a rare event.

Dust is the problem for magnetic media.

SyQuest make a big deal about their use of standard hard disk technology for their removable drives. As a selling point, though, it’s dubious. Indeed, standard hard disk technology is fast and cheap. But hard disks are hermetically sealed to keep out dust, smoke and anything else that might interfere with the fabulously fine adjustment that lets the 1.3 gigabyte SyJet fit something like 35 megabytes of data onto each square inch of its disk surface. You could store the complete script of Reservoir Dogs on about three square millimetres of its surface. When you’re talking about super-dense storage like this, one dust particle is a disaster.

Older SyQuests weren’t so susceptible to dust and smoke contamination, because they had lower data densities. The old 5.25" 44 and 88Mb carts are quite reliable, though their age can make them flaky now. The 88s are still quite popular, since they work in the more recent 200Mb drives, which themselves are not prone to errors. The 200Mb 5.25" SyQuest has data densities of around 5Mb per square inch.

SyQuest try really hard to keep dust out of their carts. Current carts have internal spiral ribs over the disk surface that channel air currents outward, taking dust with them, when the disk is spun up prior to the read/write heads swinging in. Iomega’s carts are billed as being more dust resistant, but no real comparative evidence is yet available.

SyQuest have a five year replacement warranty on their cartridges. If one fails in that period, they’ll give you another. This is better than nothing (if you can be bothered replacing your dud cart), but when a cart dies replacing it is not generally your first priority. Your first priority is checking your last backup to see how old your last copy of that data is.

SyQuest have made a big deal about the reliability of the SyJet, implicitly admitting that reliability is a big issue for consumers who’ve heard bad stories bout the 270 drives.

It all comes down to care and luck. If you’re careful with your cartridges, handle them only as instructed, don’t drop them, put them back in their padded cases religiously after use, don’t smoke near the drive and carry your lucky rabbit’s foot, modern super-capacity SyQuest storage should be perfectly adequate.

If, on the other hand, you want a cartridge you can tread more or less like a floppy disk - forget SyQuest. We don’t use them here (aside from an antique 44Mb drive for compatibility’s sake), after several nightmarish experiences with defective 270Mb drives. On the other hand, we also know people who’ve got 270s that have worked like a charm for ages.

Actual hard data on the real-world relative reliability of removable storage is nonexistent. When a person reports his SyQuest blew up, or his Zip trashed a cart, this may be because he did something moronic, or may be because of a power surge he didn’t know about, or may be because the device in question really was defective - which may or may not reflect accurately on the overall quality of the product. More people use SyQuests than any other removable storage medium, so you’d expect more horror stories about lost data and defective drives - and that’s what you hear. But more home users - inexperienced computer operators with children - use Zips than any other removable storage device, and horror stories about Zips are notable for their scarcity. There are also remarkably few bad tales about magneto-optical drives and Bernoullis - and more than a few look-what-it-survived stories about the latter. The Jaz, SyJet and PD drive are all too new to have a decent base of evidence, anecdotal or otherwise.

CD-R may be useless for scratch storage of information you want to change, but the discs approach the toughness of ordinary stamped CD-ROMs, they’re cheap per megabyte and they’re small and easy to store. This makes CD-R a fine archival format for the files you’ve finished with - after the job’s over, dump it all to a CD-R, make a second copy to store off-site, and you’re done. The shelf life of CD-Rs is unknown, but if they’re not left in the blazing sun or physically mutilated they should last until drives capable of reading them are a rarity.

The upshot? Zip, CD-R and MO are tried and tested and reliable. Old SyQuests are not reliable. New SyQuests may or may not be reliable. The Jaz seems likely to be reliable, but the jury’s out. You be the judge.

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Three technologies

There are three basic systems used for data storage in erasable removable drives today - magnetic, magneto-optical and phase change.

Magnetic media work the same basic way for all their many applications, from a 1.4Mb floppy disk to a 30Gb hard drive. A very small induction coil is held very close to a ferromagnetic coating on a disk. The drive reads data by measuring the minute current induced in the head by the passing magnetic regions under it, and writes data by passing current through the head itself to induce a magnetic field. Magnetic media have the advantage of speed, because the heads are very small and light, but the tiny tolerances involved make them more susceptible to vibration and contamination.

Magneto-optical uses a combination laser/magnetic system to read and write data. The disks have a special alloy laser whose optical properties change when it’s magnetised - but which can only be magnetised when it’s been heated by a laser. Data is read with the laser at low power.

Magneto-optical drives are slower than plain magnetic designs, because the laser/magnetic heads are heavier and take longer to be accurately moved around the disk and also because current technology has to erase a disk sector in one pass and then write to it the next, making write operations inherently half the speed of reads.

The youngest removable drive technology is phase change, presently only used in the Matsushita (Panasonic) PD drives and licensed clones, which use the same mechanism. These use a pure optical system; the recording layer can be set to more or less reflective "phases" by different sorts of heating and cooling. In theory, phase change media should be able to take advantage of smaller, lighter optical heads to approach magnetic access times, but the present PD drives are as slow to find data as recent CD-ROM drives. There’s nothing wrong with the transfer rates, though, and writing is no slower than reading.

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Parallel or SCSI?

Mass-market removable drives, like the EZFlyer and the Zip, come in SCSI and parallel interface versions. Macintosh users, if they check the backs of their computers, will note that they do not have a parallel port and will realise that these drives are aimed solely at the IBM compatible market.

Parallel drives are notably slower than SCSI, but if you’re a PC owner who doesn’t presently have a SCSI card and wouldn’t mind saving the $150 or so for a bargain basement one, they can be a perfectly acceptable compromise. They’re also excellent if you need to move the drive between different machines; every PC’s got a parallel port, and passthrough connectors mean you can still use your printer while the drive’s plugged in. Parallel drives are also handy for laptop users.

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Integrity tests - got a spare hour?

Windows 95 has a fixation about doing integrity checks on removable media after formatting; other operating systems are more polite about it. Scanning for errors can be a very good idea with SyQuest-style cartridges that have a few miles on them and could have dropped a sector or three, but when using less finicky removable cartridges or anything new out of the box there’s little danger of data loss. When you consider that it takes two hours of system paralysis for Windows 95’s ScanDisk to thoroughly check one side of a 2.6Gb magneto-optical cart, the incentive to be super-safe diminishes considerably. Dud sectors on a cart will generally become obvious as soon as you try to write to them. Unless you’re using the cart as a system scratch drive this will probably be an annoyance rather than a disaster - you won’t lose any data, because you wont be able to get it on there in the first place.

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