SCSI card round-up

Introduction

A while back, Steve Jobs announced what many thought was the death of SCSI on the Mac. Although out of favour with the Apple mandarins, SCSI lives on – and actually goes from strength to strength. Now that it’s not a pre-installed logic-board resident, SCSI capabilities are sought-after by a range of users. Some want to retain compatibility with older peripherals, some users want the fastest data-transfer rates available, and others need super-safe RAID arrays to ensure data security. We took a look at what is out there for SCSI-less Macs. The first implementation of SCSI found on the Mac was SCSI 1. It was capable of data-transfer rates of around 5MBps, compared with 160MBps in modern high-end SCSI cards. It was introduced in 1985, making it one of the longest lasting interfaces around and giving it great compatibility advantages. Old and new If you simply want to stay in contact with old SCSI devices a cheap SCSI card will do. Any SCSI card will do the job, though having the right cables is always important. It’s likely that if you’re connecting old SCSI equipment there’s probably a bag full of old cables lurking somewhere near your computer. Formac offers an ideal solution for old-&-new connectivity – the Pro Raid Lite. It’s a fast-SCSI card with an adaptor to let it connect to old 50-pin SCSI cables. If you get a faster SCSI device, simply get a new cable. The other exciting thing to note is it costs under £50, rather than the £250 for other Ultra SCSI cards. At the other end of the scale, Ultra3 SCSI offers super-quick data transfer. A subset of Ultra3 SCSI is also known as Ultra160. Both offer 160MBps throughput. The Atto ExpressPCI Ultra3 card was the fastest we looked at, with a massive 160Mbps per channel, and it has two channels totalling 320MBps – more than enough for most people. If high-end video production or music is your game, a fast drive and SCSI card are important. However, there is a basic rule of thumb: don’t get a card that’s faster than the drive needs, unless you’re using an array. A drive capable of 40MBps will get no benefit from an Ultra160 card beyond its normal 40MBps. Drives rarely perform at the optimum quoted speed. Don’t let this put you off fast cards, because faster speeds are possible using a RAID set-up. To use RAID there must be at least two drives, preferably more. There are various types of RAID set-up, but they fall into two main categories – RAID for speed or RAID for secure data. At its most basic, RAID 0 (for secure data) is simply two drives that are mirrored. Every time something is saved to disk, it’s automatically saved on the second disk too. If a drive fails there is always a back-up available. For the fastest speeds available, choose RAID 1. This uses two or more drives in unison to act as a single drive. As the data is recorded it’s directed to the drives in turn, so that no single drive has too much data to handle, which can cause a bottleneck. It also means that slower drives can be used to achieve fast data transfer. Other RAID configurations are possible, but are more specialized and often need special hardware controllers. These combine the safety of RAID 0 and the speed of RAID 1, but need as many as four drives to work. They are available from specialist storage companies, such as Micronet (www.micronet.com, or ring United Digital, 01926 810 000). The company that offers the widest choice of cards is Adaptec. We looked at only three of the cards. Adaptec supplies clear and easy-to-understand manuals, and usually the correct internal cables – though it’s worth checking if the cables are correct for your drive. Adaptec’s Ultra160 card lacks some of the features of the Atto Ultra3 card, but the differences are minimal. We tested two Atto cards. Both feature ADS technology, which Atto claims reduces the amount of bandwidth needed to transfer data. The fastest card on test was the dual-channel Ultra3 card, with 320MBps theoretical throughput – but few people would use that kind of bandwidth. At almost £455, I was disappointed at the lack of cables and the skimpy manual. The bargains of the bunch were the Formac cards. Both the Pro RAID (£59) and the Pro RAID Lite (£45) offer 40MBps. The difference being that the Lite version comes with a 50-pin SCSI adaptor for connecting to older SCSI devices and the Pro comes with internal cables.
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