Brian says:
Ahh Yess... SCSI I, SCSI II, SCSI III, SE, DF, Wide, Narrow, Fast, Ultra, LVD/SE, HVD, Ultra160 and Ultra320...
I know I am forgetting a couple of others.
Ultra2 and Wide Ultra2
A little trick that support showed me when dealing with LVD/SE external devices is;
Use a SE Terminator on a LVD/SE device to force the bus to SE. And always use the proper active terminator.
My understanding is SE mode is slower than LVD mode, therefore not taking advantage of the drives capabilities.
I prefer to use an external Terminator then internal terminators with jumpers. One issue that I have run into a lot lately is people re-using SCSI cables. Customers do not like to fork out money for new scsi cables when they purchase new gear. The issue is; the old cable was designed to run SE SCSI at 10 to 20 MB per sec. New SCSI devices running LVD/SE or HVD can run at 40, 80, 160 or 320 MB per sec and the old cables can't handle the throughput and cause all kinds of intermittent problems. Just because the connectors fit does not mean you have the right cable.
OK on the cable advice, but wouldn't one only use an external terminator in an application where an external, (like, outside the box) application calls for one? External terminators all have the locking screws, internal terminators are made to slide onto internal ribbon connectors. You lost me here.
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At 07:28 PM -0400 10/11/2004, MikeRF/A2 wrote:Can someone here verify this:
"The terms active and passive were used for SCSI through SCSI III UW. When LVD/SE and LVD devices entered the market, termination had to be re-invented, as neither active nor passive would work for all applications. If you place an LVD/SE drive on a SCSI III UW chain, an older SCSI III active terminator may work, but has just as much chance of not working."
Yup.
Seagate tells me I need "active negation" termination on my LVD/SE SCSI Cheetah drive. The drive itself provides no means for termination.
Odd. All drives that I've used have some form of termination available onboard, be it enabled by jumpers or with a flat-pack. If the drive is SCA, then the SCA Adapter will have termination pins.
What's the exact model? What are you plugging it into?
It's a Seagate Cheetah 18 GB ST118202LC (SCA 80 pin)going to an ATTO ULD2 (Ultra2 Wide) controller. Here is what Seagate says about this drive:
"Due to the specifications of Ultra2 SCSI, Seagate LVD drives have no provision for setting termination on the drive. Termination must be provided by an external source. Similarly, termination power is hard locked to "Drive supplies the Bus" and can not be changed. Although compliant with LVD controllers, these settings may not be fully compatible with standard Single-Ended SCSI controllers."
In addition I have an SCA 80 to 68 (or 50) adapter that does not provide termination. My cable came included with an inexpensive LVD/SE terminator which doesn't seem to work. I have only seen the drive on my Beige 266 rev 1 MT /10.2.8 when using the built-in SCSI connected to the 50 pin out on the SCA adapter with an old 1 GB SCSI drive from my junk pile at the end of the chain. The 1 GB drive hanging out the side of the box notwithstanding, I will not waste the capabilities of this drive using it in this 8 bit SCSI 1 mode.
Every time I turn around someone redefines the SCSI terminology I thought I had figured out, making me crazy.
No, it's not changed in years. But perhaps you're using newer technologies now and running in to these issues.
Well, on the one hand I'm told by Seagate I need an active terminator (actually active negation) for my LVD/SE drive, then told active/passive doesn't mean anything for terminating LVD/SE devices.
>Every terminator specifically stating it provides "active negation"(not many) costs as much as I paid for the drive.
ug. Check CyberGuys.
Re-checked CyberGuys catalog again last night. Nothing described as "active negation." AGAIN I'll pose the question, Is active negation really necessary or just overkill on Seagate's part to insure the best data rate? It's a short internal cable. Maybe it's another of these SCSI terms being loosely thrown around to keep people confused?
Thanks, Mike
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