aad@stepstone.com (Anthony A. Datri) (02/03/89)
brian@natinst.com (Brian H. Powell) writes: >Near as I can tell from the disk drive docs, you can either hook up the >A-cable as a daisy-chain configuration or a star configuration. (And you >have to terminate the end(s).) The Sun documentation I have even has a picture of how to cable, and they show a data cable going from the controller to each drive, and the command cables daisychaining. That command cable is something like a 60 pin berg connector, and in my fairly limited experience I've never seen a controller that had more than one command connector. In short, daisy chaining them seems to be the right thing to do. How many total disks are you running off that controller? Four disks off of one controller aren't going to give you quite the max aggregate throughput of four disks off of four or even two controllers, but unless you're accessing the hell out of every drive on that controller I wouldn't be that concerned about it. >If we don't daisy-chain, any suggestions on how to make the cable? Any >tricks to it? If you didn't daisy-chain, what would you do, make an octopus? That'd be pretty much the same electrically, I think. The SMD drives I've seen have dip switches to set the unit number, so the unit number would seem to be a couple of those command signals. Ah for the days when drives had unit select plugs on the front... >Also, does anybody know what you call those connectors that are on the >Xy753? I'm used to DB connectors with nice big pins. I haven't ever seen >those small tight pin jobs before, so I don't know what to ask for. I've never seen a 753, but if they're like just about every other board made in the last 15 years, it's what DEC calls a "Berg" connector. Many of the connectors on DEC stuff actually do say "Berg" on them, and most people seem to call them that. I once spoke to someone who got very perturbed with me for calling them that. He didn't have a very memorable alternative. -- Anthony A. Datri @SysAdmin(Stepstone Corporation) aad@stepstone.com stpstn!aad
shj@ames.arc.nasa.gov (Steve Jay) (02/09/89)
In v7n134, aad@stepstone.com (Anthony A. Datri) says: > I've never seen a 753, but if they're like just about every other board > made in the last 15 years, it's what DEC calls a "Berg" connector. I have seen a 753 (we just installed one), and it does not use a "Berg" connector. They look like miniature DB connectors, and the cables we got just clip on, with buttons to squeeze to release. I don't what they are, but I like them: no tools needed, seem to be reliable, and the cables themselves are thin & flexible. If only we could get Ethernet tranceiver connections with the same cable & connector. As to the original question, with a 753 you must daisy-chain the A cable (only one A cable connector on the 753), and terminate the A cable at the last drive. As I remember it, the total length of the A cable must be short - 15 or 25 feet max. All the disks must be close to the controller, and use minimum length segments to go from drive to drive. Whoever you buy drives from should have details. Steve Jay domain: shj@ultra.com Ultra Network Technologies Internet: ultra!shj@ames.arc.nasa.gov 101 Daggett Drive uucp: ...ames!ultra!shj San Jose, CA 95134 408-922-0100