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Re: External HA disk enclosure A3312A connected to a V2500

 
pj_11
Super Advisor

Re: External HA disk enclosure A3312A connected to a V2500

The information provided by Forum resloved
my problem.No terminator on internal scsi connector.Thanks once again surely not my last post.
Steve Post
Trusted Contributor

Re: External HA disk enclosure A3312A connected to a V2500

I don't think it should be called a terminator in my opinion. It should be called a dampener of reflections.

The terminator really is a signal dampener that keeps the data signal from bouncing BACK along the scsi bus.

Why do I bring this up? Because it sounds weird that you "terminate" the scsi cable just as it LEAVES the box. The terminator does NOT terminate good data. The terminator stops good data from reflecting back.

Think of two guys with a rope stretched out between them. One guy pokes the rope. It makes a wave. When it hits the other end, the wave bounces back toward guy 1.
Torsten.
Acclaimed Contributor

Re: External HA disk enclosure A3312A connected to a V2500

Steve wrote:

"Because it sounds weird that you "terminate" the scsi cable just as it LEAVES the box"

This card have an internal and an external connector for the same bus. Both ends have to be terminated. That's all!

Hope this helps!
Regards
Torsten.

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timmy b.
Honored Contributor

Re: External HA disk enclosure A3312A connected to a V2500

Two guys and a rope isn't the best analogy. A water pipe is better. If you don't have end caps screwed on, the water all drains out onto the floor. In the case of the SCSI bus, the lost bits flow into the proverbial Bit-Bucket. Trust me, it's much easier to clean up a water spill than lost data!

Good humor, guys. Thanks Steve, now I'm going to see little Arnold Schwartzenegger faces every time I see a Terminator....
There are 10 kinds of people in this world: Those who understand Binary, and those who don't.
Torsten.
Acclaimed Contributor

Re: External HA disk enclosure A3312A connected to a V2500

Just for clarification + @steve:

As we all know, a scsi bus have to be terminated on both ends.
One end is the last disk. There have to be a terminator.

the other end (or the beginning ;-) can be auto-terminated by the controller or terminated by a terminator.

in this case, there have to be a terminator on the internal connector, because it is only one bus.

in high availability environments (multi-initiator, to servers are sharing one bus) special cables (called inline terminated) are used. The terminator is inside the cable just in front of the controller. It is safe now to disconnect the cable while the other server is using the bus.

Hope this helps!
Regards
Torsten.

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Steve Post
Trusted Contributor

Re: External HA disk enclosure A3312A connected to a V2500

Thanks Torsten.

I actually have those self-terminating cables. They're about two feet long, and black.

I like the plumbing comment above. All I can now think of are imaginary "bit" buckets.