Noel

SCSI and Termination: help!

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It's hard to fathom, but I have been using 3 SCSI drives for 4 years in my desktop and really don't have a clue what I'm doing! I added a 4th drive and I am almost ashamed to say used the trial and error method to set up jumpers so the 4th drive would be recognized (!!). I have been operating under the belief that I did not need to consider this "termination" issue and I find a few articles I've read to really not improve my understanding of the issues with this.

Can someone put me in touch with an "idiot's guide to SCSI" in web article form? Or just explain what I need to know in simple terms?

Here is ALL I have in my SCSI system, ie I have no other SCSI devices:

4 U320 Seagates (3 are 15K, 1 is 10K, not that this matters I believe!)

1 LSI1010 U160 controller in a regular PCI slot

Here are my questions, and if you can answer them then I may remain blissfully ignorant of all the other SCSI concerns, as I have done so far! I guess I can contact SEAGATE, whose tech support may be able to reduce my questions down to short and effective answers.

1. Is there any need to specify which device is "terminated", or is this automatic or P&P?

2. What do I need to know about "parity"?

3. If I picked up a U320 controller that plugs into a standard PCI slot, will I gain anything in transfer rates over my current card?

Obviously if my system is working, something must be set up correctly. What has made me post this distress call is that when I put on the 4th drive a few weeks ago, simply specifying a SCSI ID did not lead to the controller's BIOS picking up the drive, in fact it was an either or situation: with the new drive added, two others DISAPPEARED! I ended up dinking around with some jumpers and I really wasn't certain exactly what I was doing.

Anyway, I'm guessing that a few pearls about these issues could reduce down the critical knowledge deficits enough where I could be confident I . . .knew what I was doing enough to set up THIS system.

Seriously, any help would be appreciated, especially short and concise help. As you can tell, I'm trying to avoid becoming an expert in all matters SCSI, and really don't wish to go into SCSI vs SATA or any other tangential concerns. I'm guessing a few simple pearls like this will be all that I need: 1. Set an ID using jumper for each device, 2. Set the jumper to TERMINATE on one of the devices, and leave the others to not terminate. Is this it?

Many thanks in advance,

Noel

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1. Is there any need to specify which device is "terminated", or is this automatic or P&P?

If you have one end of the cable connected to the controller, and you have a terminator on the other end of the cable, then termination, if any, should be disabled on the drives.

2. What do I need to know about "parity"?

This applies to RAID setups. Parity is essentially extra data calculated from existing data, which is used to recover data if one or more discs fail. Some RAID levels use parity caluclations, such as level 5, while some don't, like level 0. Are you currently running the discs in RAID?

3. If I picked up a U320 controller that plugs into a standard PCI slot, will I gain anything in transfer rates over my current card?

Not really. U160 (160MB/sec) is already faster than the regular PCI bus (133MB/sec).

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3. If I picked up a U320 controller that plugs into a standard PCI slot, will I gain anything in transfer rates over my current card?

Not really. U160 (160MB/sec) is already faster than the regular PCI bus (133MB/sec).

Thanks for those answers. A question I have also is that when I run HDTach it's showing average read times of 90mb/sec. Is this because my LSI controller is sitting in a 32-bit regular PCI slot? Would a new card that goes into a PCIe slot and says U320 single channel get quite a bit more average read rate?

Thanks again P

Edited by Noel

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3. If I picked up a U320 controller that plugs into a standard PCI slot, will I gain anything in transfer rates over my current card?

Not really. U160 (160MB/sec) is already faster than the regular PCI bus (133MB/sec).

Thanks for those answers. A question I have also is that when I run HDTach it's showing average read times of 90mb/sec. Is this because my LSI controller is sitting in a 32-bit regular PCI slot? Would a new card that goes into a PCIe slot and says U320 single channel get quite a bit more average read rate?

Thanks again P

Yes, you'd get a better transfer rate out of a PCIe slot; though a 1x slot will give you only 250MB/sec, theoretically. You might be able to raise the figure of 90MB/sec to a bit higher by increasing the PCI Latency Timer, if your motherboard supports it. On my ASUS P5B, for example, I can get a burst transfer rate of 112MB/sec, on a U160 controller (Adaptec 29160).

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3. If I picked up a U320 controller that plugs into a standard PCI slot, will I gain anything in transfer rates over my current card?

Not really. U160 (160MB/sec) is already faster than the regular PCI bus (133MB/sec).

Thanks for those answers. A question I have also is that when I run HDTach it's showing average read times of 90mb/sec. Is this because my LSI controller is sitting in a 32-bit regular PCI slot? Would a new card that goes into a PCIe slot and says U320 single channel get quite a bit more average read rate?

Thanks again P

Yes, you'd get a better transfer rate out of a PCIe slot; though a 1x slot will give you only 250MB/sec, theoretically. You might be able to raise the figure of 90MB/sec to a bit higher by increasing the PCI Latency Timer, if your motherboard supports it. On my ASUS P5B, for example, I can get a burst transfer rate of 112MB/sec, on a U160 controller (Adaptec 29160).

Yes PCI Latency can help. There are even Windows-based tools to change it, such as the creatively named "PCI Latency Tool".

Phoenix answered your termination question. It's needed on both ends of the cable (as in for example card and terminator on the end of the cable). Adding another drive somewhere on the cable changes nothing, if it worked before it'll work now.

So back to the jumpers. I suppose these are 68pin SCSI drives (do you use an adapter, or do they plug direct into the cable?). Assuming for a second they are 68pin, the jumpers set the SCSI IDs. Thus, if the drive you added was set to use the same ID as another drive, this is why others disappeared (conflict). What you really need to do is read on the drive itself which jumper positions/combinations lead to which SCSI IDs, and set _unique_ ones for each drive.

Good luck.

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And the last drive next to the termination (and only this last drive) should have a jumper for term power enable. This should probably be enabled, it assures adequate power gets to the termination. Sorting out any id conflicts is also a good idea.

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