68 pin versus 80 pin scsi ??

[Soulkeeper]

I just got a few quick questions
is there any difference in performance ?
which one is better and which one came first ?


thanks

 

[BD231]

80pin drives are hot-swap and mostly used in servers. They have no molex connector and require an adapter to run on basic 68 pin SCSI cards.

The only difference between the drives is interface.

PS: The extra pins provide the power, nothing more.

 

[xenos500]

yea its the same....
you cant use an 80 pin in your computer (without an adapter) unless it has a scsi backplane that uses 80 pin.

 

[Skoop]

There are various flavors of these adapters, it appears. Some have 9-pin negation, some are terminated, etc.

How are these various kinds used?

For an LVD 160 drive with an 80 pin SCA connector, what kind of adapter is used to simply connect to a terminated 68 pin cable that has other 160 drives on it and is terminated?

Also, is there any degradation in performance by using an adapter?

 

[Gouv]

I'm actually facing this problem right now. I bought an SCA adapter that's terminated, but it's not LVD compliant. I can't run the drive in Ultra2 SCSI LVD mode, but I'm not sure if it's the adapter or my SCSI card. I ordered an LVD compliant SCA adapter to see if it makes a difference, and we'll see what happens.

Does anyone know from experience if there are differences between these adapters and also between Ultra2/160/320 cables and regular ones?

 

[sharkeeper]

If you're starting from scratch, SCA all the way! Hotswap is *the* way to go especially if you plan to run more than two SCSI disks. Having quick access to your drives from the front of the machine is a big plus. If you're running four or more drives, it's silly to bolt them in!

Recommended

LVD cables differ from SE cables by a twist to reduce crosstalk at higher data rates.

Cheers!

 

[Gouv]

Just to update:

The U160, LVD compliant SCA adapter made a difference. Now I can use the Ultra2 SCSI controller on my adapter.

 

[addragyn]

SK I posted this in a [l=http://forums.anandtech.com/messageview.cfm?catid=45&threadid=1265404&STARTPAGE=1&zb=902688]FS/FT thread]. I had a hard time finding basic SCSI info when I was looking. HTH

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SCSI can seem very confusing initially. Here are some basics that would apply to getting a drive going.

SCSI is backwards compatible. You can run a U320 drive on a U160 cable on a U2 card.

Every SCSI device in the chain has an ID. Your HBA(SCSI card) is typically 7. Most newer HW will take care of the ID business for you.

Each SCSI chain must be terminated on both ends. The HBA will terminate the end it is on and your cable will have a terminator on the other end. Not all terminators are made equal. There is junk out there and it can/will cause problems.

SCSI connections are commonly in 3 varieties. 50 pin is used by older equiptment and is sometines used on external stuff. 68 pin is the most common. VHDCI is a type of external 68 pin connector. 80 pin or SCA is used in SCSI back planes where drives can be hot swapped. 80 pin carries power. You can get adapters to use an 80 pin drive with your 68 pin cable. It will be a circuit board that will take your 68 pin and power connector and get it all into your 80 pin drive.

LVD is Low Voltage Differential. Is is the signalling scheme used by Ultra2, U160 & U320.

When you buy a SCSI cable it will specifiy how many devices. This number is counting all plugs on the cable. That includes your HBA.

Do not plug unplug SCSI stuff that is not setup fo hot-swap when power is own. SCSI carries power. LVD, low voltage differential, get it?

HSW has a good article: http://computer.howstuffworks.com/scsi.htm

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