Thanks a bunch, Ed. As is usually the case, you have provided all the information needed and then some.

I had stayed away from PC tape drives because a friend had a bad experience, but your points are important and I will definitely look into one for the new machine. I had been 'satisfied' with alternate drive backups of crucial directories, but that needn't cancel out tape.

I'll need to digest the balance of your reply as well as investigate a few things before buying anything. Bragging rights are of no interest if the actual performance doesn't match, so it looks like I'll be saving myself some bucks once I fully understand these relationships.

Thank again,

Jim N



>>But I've also had a real streak of bad luck, losing 3 HDs (2 different machines) in the last 14 months. So I'm also looking at these nice cheap HUGE ultra-66 jobbies, first as a C: drive but also as a place to backup stuff on the SCSI drive(s) I would have there.
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>Hopefully, after losing drives, you'll make the decision to invest a small amount of money in a tape drive. You can't physically remove the hard drive and store it elsewhere, it's prohibitively expensive to maintain multiple backups, and physical damage or theft of the machine leaves you unprotected.
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>>First problem... on the DELL site I cannot even configure a system with a combination of ultra-66 and SCSI. Seems to me it should be a valid thing to do. Is there something preventing doing so??? Or might it be a dumb thing to do for some reason???
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>They probably do not have a system configuration that includes both. You can always add n adapter like the Adaptec 2940U2 to add a UW2 SCSI channel. Boards with on-board SCSI (like the SuperMicro boards I use for servers and NT systems for myself) are not commonly available from places like Dell, because the people interested in buying them don't represent a large enough market.
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>>A second concern is the performance impact of adding "older" (slower) devices on the EIDE or SCSI 'channels'...
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>EIDE channels run in the mode of the least capable drive, so mixing older drives operating at lower EIDE clock rates will slow the burst transfer rate of the channel. EIDE cannot perform overlapped I/O (it doesn't have the equivalent of the Disconnect/Reconnect protocol, or tagged command queuing features of SCSI) so only one device can be actively in process at any single time. I don't see either as a major issue unless you're running a heavily loaded NT or Win2K system with enough I/O distribution to keep multiple targets busy. Since none of the drives on the market now can transfer data to and from the drive itself at anything approaching half the 66MHz Ultra-66 EIDE channel rate, except for very old EIDE stuff, it's not worth worrying about.
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>SCSI devices negotiate the best supported rate between the drive and the HA independently, so older devices don't have the same effect on overall bus performance. As long as the drives support the SCSI-2 Disconnect/Reconnect and TCQ operating modes, you can have multiple drives with work in process at the same time on a channel. The sole consideration here is that if you buy Ultra2 SCSI LVD drives to work on a U2 channel, and hook any non-LVD drives to the channel, you have to operate the channel as a 40MB/sec Ultra-Wide channel, because of the presense of single-ended devices - it's a matter of the electrical limitations of the single-ended bus interface.
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>>I would buy a new SCSI (10,000 rpm, 80mbps) but I would like to put the 2 SCSI drives from my old system into the new box too. The question is, would this have any impact on performance of the new faster drive? That is, would this cause the adapter to operate at the lowest common denominator speed?
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>Jim, since even the 10K U2 Cheetahs don't move data at anything approaching the 40MB/s of a Ultra-Wide channel, it's not a real issue. Again, without Win2K or NT keeping multiple drives on the channel busy iusing something like a stripe set, it has no practical effect. The channel bus clock speed for unsophisticated workstation environments with routine workloads aren't an issue for anything other than bragging rights. You need multiple targets active in process on the channel to come close to loading the SCSI bus.
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>You might want to look instead at adding something like the big Seagate Elite drives - at least one vendor I use (CSC) is selling the 5400RPM 47GB Elite for about $700 new in an external enclosure. That's less money than you'd spend on an 8GB LVD Cheetah. www.corpsys.com
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>>As for the EIDE side, I would have the same concern regarding having a CD-ROM or DVD mixed with it. Any impact on speed of the faster HD?
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>Again, it's a matter of lowest common denominator for EIDE, and only one device can be active at a time. OTOH, most systems have two EIDE channels, supporting up to 4 drives. Again, channel clock speed is bovine fecal excrement. The drives can't move data off the platters at anything approaching 20MB/sec IAC.
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>>I also understand that EIDE typically comes with 2 separate 'sides' (I don't remember the technical term). If that is so, could one configure the HD on one 'side' and the CD/DVD on the other, and would that help performance of the HD?
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>Channels, and yes, each channel is independent of the other, so a drive on channel 1 is not affected by the devices on channel 2. If the second device on a channel is relatively slow (since there's no disconnect/reconnect, it is an issue for CD/DVD, where seek times can approach 100ms) and there's no overlapped I/O on the channel, simultaneous operations to both the hard drive and CD/DVD might be an issue.