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What To Look For
Recommendations

Already know what a SCSI Card is and what to look for? Then skip to the Recommendations. 

What To Look For:

• The type of controller is the most important thing to consider.  If you want a controller for hard drives, you might as well get the Ultra320 controller since there isn't much of a price difference (if you find one significantly cheaper that's Ultra160, it should be sufficient). If you want to get a controller only for CD-ROM / CD-RW drives, then narrow SCSI (50 pin internal connector) is all that is needed.
• Transfer rate is another thing to consider.  These are usually determined by the type of SCSI card, which can be SCSI-1 (10 MB/sec Max), Narrow SCSI (20 MB/sec Max), Wide SCSI (40 MB/sec Max), Ultra2Wide SCSI (80 MB/sec Max), Ultra160 SCSI (up to 160 MB/sec Max), and now Ultra320 SCSI (up to 320 MB/sec Max). Before you jump to conclusions and determine that Ultra320 is a must have since it is "twice as fast" as Ultra160, be warned that the two controllers will yield no speed difference when only 1 hard drive is connected.  You might not even notice the difference with 4 hard drives connected. 320 MB/sec Max simply means that all drives on the card can transfer a total of up to 320 MB per second.  Since 1 drive will not currently transfer data nearly that fast, it's pointless for a single drive. However, if you have 10 drives in a heavily accessed server, the 40 MB/sec limit of Wide SCSI may actually slow things down.
• Number and type of connectors are obviously important. If you get a 68-pin Ultra320 drive, you want to have a 68-pin Ultra320 connector on the SCSI Card (although a 68-pin Ultra160 connector would be sufficient - even a 68-pin Ultra2Wide or Ultra2 connector would work if you have something to terminate the chain).  If you've got an external Narrow device, then you need a 50-pin connector on the external portion of the card (this may be used for scanners or external CD burners).  However, there are adapters to get around these problems, but they are not always 100% effective (not to mention that you lose out if the device is (for example) a 50-pin device and you try to connect it to a 25-pin port). 
  If you are looking for a SCSI controller that will do it all, you want to have an internal 68 pin connector (preferably Ultra320) for hard drives, an internal 50 pin connector for CD drives, and an external 50 pin connector for scanners and other devices (or external 68 pin connector for additional hard drives).
• The Chipset on the SCSI card is also important, but I don't know a lot about the chipsets.  I DO know enough to say that the Tekram and Symbios Logic chipsets are good (and can be found quite cheap) and Adaptec's chipsets are considered to be the best.
• Some motherboards have SCSI controllers on them. If you're getting a whole new machine, this may be the way to go if you want SCSI.  The motherboards are more expensive, but it is less expensive than buying a SCSI card. The only problem is that if you decide to get a new motherboard later on, you can't take your SCSI controller with you, but you could if it were a separate controller...  Thus, you will spend more in the long run if you plan to upgrade your computer like that.
• If the SCSI controller is going to be used for a large number of hard drives, getting a dual channel card may be helpful.  This can provide a speed increase in addition to supporting more devices. Have a dual channel SCSI card is kind of like having 2 SCSI controllers in one computer (2 of each connector usually).
• If you're getting a RAID controller, be sure it supports the RAID levels you need. RAID 0, 1, 5, and 0/1 are the most commone levels that you would want supported on your RAID card.

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