Cluster Q&A: SCSI Termination

July 11, 2002

SCSI Termination

Question:
Is a separate SCSI Card needed for the External SCSI case or is this
External device just a part of the SCSI-Chain between the two nodes (the
Endpoints of the SCSI chain are the two nodes)?
Answer:
Yes the termination happens in the nodes and Termination is disabled on the external drives (or enclosure).
Question:
Is the Meaning of a external SCSI enclosure will have the Y cable built in
internally the same as the SCSI Drives of this External case are terminated
internally?
Answer:
No, See above for proper way (node termination).
The reason is that both computers (nodes) have to be on the same SCSI Bus so they can both see the drives. Then they use SCSI Disconnect and Connect to talk to the drives one node at a time.
Each time they connect, each node reads the FAT off of the drives.

Leon

Posted by Leon at July 11, 2002 02:01 PM

Comments

Dear Sir:
It is so difficult to understand what you said above.

I have two PC with MS advanced 2000 and PC-SCSI card; one external array with one SCSI.
Currently I connect one end on PC; another end on External Array and one terminator is also on
the external array (One SCSI Drive has two female connectors). It is working. I can see the scsi drive by disk management on PC.

Now How I can connect this external array to my another PC?
Thanks.

Posted by: jianxin zhang on April 2, 2003 06:10 PM

Hi Jianxin,

I have a couple of diagrams for you to look at which, hopefully, will clear up your confusion.

This one shows various hardware configs:
http://www.leonletto.com/images/cluster_configs.gif

This one is a concept showing virtualized IP's and names.
http://www.leonletto.com/images/microsoftclusterdiagram.gif

Keep the questions coming!

Leon

Posted by: Leon Letto on April 2, 2003 09:35 PM

Leon,
I'm very interested in seeing your diagrams but the site is not up. Can you e-mail me with them?

Posted by: rhonda on May 7, 2003 10:54 AM

I'd like to see a 3-node diagram.

Thanks,

Yong

Posted by: Yong Di on October 20, 2003 10:34 AM

The diagram for a three node is the same as for a two node (with an additional Y-cable). the caveat is taht you have to make sure that your SCSI controller can have one of three SCSI ID's (many only support 6 or 7 (2)). Then all three nodes sit on the same bus as the SCSI drive(s).

Leon

Posted by: Leon Letto on October 20, 2003 11:33 AM