The Controller Card
Once you decide that SCSI is for you, the first item you’ll need to consider is the SCSI adapter, which is also called the SCSI controller. You want to make sure that whatever SCSI adapter you select has the ability to run non-LVD devices (such as burners, scanners, CDROM & Zip drives) without degrading performance of devices running on the LVD channel (i.e. hard drives).
Mixing LVD (or U160) devices with non-LVD rated devices (on the same channel) will cause your LVD devices (hard drives) to run at non-LVD speeds (max 40MB/s, in what is called Single-Ended mode). Altho you can run SCSI devices configured like this, this configuration is not optimal.
LVD is an acronym that stands for Low Voltage Differential. It offers performance enhancements that you definitely want in your system. Most notably, the ability to transfer data at rates of 80MB/s, or 160MB/s in the case of the Ultra160 protocol.
While adapter cards supporting nothing faster than the UltraWide (UW) protocol, which max’es out at 40MB/s, are not necessarily a poor decision, I don’t recommend them, for reasons I’ll address later. Note that in each case, actual, real-life transfer rates will be somewhat less than the theoretical maximum, taking into account things such as ‘bus overhead’.
In the case of Ultra 160, PCI bus limitations (133MB/s theoretical, 110MB/s realistic) also come into play (for 32-bit PCI slots). This means that today’s 32-bit PCI bus is able to take *full* advantage of the U2W (80MB/s) interface, but not the U160 interface (160MB/s). This is not a major point, tho. If I were purchasing a card today, I would definitely buy an U160-capable card. But if cash is tight, you don’t lose very much by opting for an U2W card.
I’m not sure if you can exceed the PCI limitation of 133MB/s when transferring data from one U160 drive to another, on the same channel (provided you have an U160-capable controller). I heard both yes & no. If someone knows for sure, let me know. This would only apply if your system contains two U160 hard drives, Again, not a major point.
A BIOS makes SCSI a Snap
Once upon a time, in the not too distant past, SCSI could be a bear (difficult) to install & configure. But with today’s BIOS-sporting adapters, it has become surprisingly simple to configure your very own SCSI-powered workstation. Like I mentioned earlier, you’ll need to become familiar with SCSI IDs & termination. But I promise that you won’t find it very difficult.
You shouldn’t take this to mean that you won’t have a few quirks to iron out. Every system is different, each with its own issues. Working thru initial configuration glitches is considered a SCSI rite of passage. If you don’t have any problems, it probably means that you did something wrong. =)
Everybody seems to have at least one initial configuration glitch that needs working thru. But I only know of *one* person who had so many problems that he gave up on SCSI entirely. And that was years ago, back when SCSI was much less user-friendly. The very act of expecting & anticipating initial-configuration problems seems to take the sting out of any problems you might actually have.
Either way, this guide will help flatten the daunting SCSI learning curve, and minimize your potential for problems. Fortunately for you, I’ve already encountered most of the problems you’re likely come across on the path to configuring a full-blown SCSI-based system.
I’ve also received reports from many other SCSI users, who’ve shared their own problems, solutions, & tips, using a variety of system configurations, with a variety of SCSI drives & adapters. In the pages that follow, I address the common pitfalls in a straightforward manner, and steer you away from them.
SCSI with Windows XP
Update: 22jan2003 - Much debate has raged across the Net regarding the use of (fast) SCSI hard drives in concert with Windows XP: Microsoft’s latest version of its market-dominating operating system. Since I am a big SCSI fan, I’ve been watching the debate and have avoided Windows XP, even tho I like it a lot [still using Windows 2000].
Much has been learned by people far smarter than me. At the StorageReview, you can find the low-down on the situation. To save you some reading time [my eyes started burning halfway thru], I’ll post a brief synoposis.
1. It’s okay to install and run Windows XP from any SCSI drive.
2. You will experience slower file transfers [~ 50% slower] in WinXP when using Windows Explorer.
3. The reason for #2 above is because WinXP’s Explorer transfers files in a more secure method [using something called a WRITE_THROUGH file flag].
4. The phenomena is only seen in SCSI drives cuz IDE drives [which most people use] don’t include the WRITE_THROUGH flag in their command set. It’s scheduled to be included at some later date.
5. Windows 2000 has a minor bug that ignores the WRITE_THROUGH command and writes the data to the (faster) cache instead of to the (slower) disk, even if the application asked it not to.
6 . You could lose data in Win2000 if you lose power while transferring a file. [I use the APC Back-ups 650.]
7. This phenomena does not affect all file transfers in WinXP when using SCSI drives - only those that use the WRITE_THROUGH file flag [such as Windows Explorer].