Data Transfer Rates

[kcidwx]

A friend of mine was trying to explain to me data transfer rates. Most of it didn't make any sense to me. I'm looking at getting either a ATA 100 hard drive or a Ultra 160 SCSI hard drive. He says the ATA interface can transfer 100mb/s and the SCSI can transfer 160mb/s. So I'm thinking why not go for the 160mb/s SCSI drive. He told me that it doesn't make any difference because hard drives are not capable of these data transfer speeds. He said the maximum a hard drive can transfer is around 50mb/s. Is this correct thinking?

Why are they even bothering with Ultra 320 SCSI then?

Thanks!

[jrb420]

SCSI does have a much faster transfer rate. I don't know the specifics of how, maybe someone else can explain. One of the buggest advantages of SCSI is that it basically uses it's own processor, instead of taking up valuable CPU bandwidth with data transfer. SCSI can also handle multiple commands at once, whereas IDE can handle only a single command at a time. Example: SCSI can read, write, fetch, and delete all at the same time without a big loss in speed. IDE has to wait for one command to finish before starting another.
Another example: Say you have 2 SCSI hard drives on the same cable and want to transfer a file from one to the other. Since the SCSI bus can handlethis all at one, it's writing directly from one to another at the same time. IDE has to fetch one piece of data from the first hard drive, then switch to the other to write it. With small files, this happens so fast you can't tell what it's actually doing.
Your friend is right in one sense, you probably will never see the max transfer rates, but the SCSI will still be a lot faster.
What it really comes down to is money. Is it worth it to spend 3 or 4 times the money on SCSI? For most common users, IDE is fine.

[kcidwx]

Thanks for the information. All this came up because I was reading about Ultra SCSI 320 and I went to IBM's web site and they have specs for their up coming Ultra SCSI 320 drives. What bothered me is that they are no faster (according to spec) then the Ultra 160 drives. My question is if the drives only transfer 50mb/s then who cares if it's on SCSI 160 or 320? It seems the SCSI bus is getting a lot faster and the drives are really lagging behind.

[jrb420]

It does seem like the drives are lagging behind. But then again, having a faster bus may help the overall transfer rate, especially if you run multiple drives on the same bus.
I am a very avid SCSI enthusist. I'm looking forward to the day when SCSI is mainstream, used in all computers. The only reason it's not is because it's so expensive, so many people don't buy SCSI. If more people bought it, the prices would come down, but since it's so expensive, most people aren't willing to fork over the cash. See a pattern?
I have several reason why I'm going to a SCSI system:
1) Faster bus and drives.
2) 15 to 60 devices on one bus, as compared to 2 on IDE.
3) Lasts longer. Most SCSI hard drives and adapters are rated at 1.5 million hours before failure. Most I've seen from IDE is 150,000. So to me it's worth the extra cash, just for the reliability.
4) Uses less system resources, reducing lag to almost nothing. The SCSI adapter I'm going to buy has a 32MB buffer upgradeable to 128. Uses PC-100 ram.

If you're serious about wanting SCSI stuff, let me know and I'll post a few links I've found for the stuff I'm gonna use.

Anyway, just my idea.

[kcidwx]

I'm definately going to build a SCSI system. The problem is that I really want to understand how the technology works before I build it. I see there are several connectors (50 pin, 68 pin, 80 pin). Not sure what the difference here is. Also I'm only going to run one HDD (maybe 2 max). I was looking at SCSI raid and it seems to me that's for servers only. I will also need a SCSI card that has an external 50 pin (I think narrow 50 pin) connector for my HP scanner. Other then that I'm open for suggestions. I'm also planning to add a SCSI DVD writer and CD writer.

My number one goal with this is SPEED!

Thanks!

[jrb420]

I don't know all he details regarding the differennt SCSI connectors and pins. I do know that if you want speed, go for SCSI-3 (68 or 80 pin Ultra160)
I looked up some links on FAQ. These may help explain some of the SCSI mystery.

HERE (http://www.awardone.com.au/tech/scsi_faq.htm#SCSI%20vs%20IDE)

AND HERE (http://scsifaq.paralan.com/)

I also have some links to some good SCSI controllers and drives.

HERE (http://www.googlegear.com/ggweb/jsp/ProductList.jsp?ThirdCategoryCode=010303) is a large selection of SCSI controller cards. You should be able to find something to suit you. Make sure to look at the max transfer rate. make sure it's at least 80MB/s or preferrably 160MB/s. Anything slower will not use the hard drives to their potential.

And HERE (http://www.googlegear.com/ggweb/jsp/ProductList.jsp?ThirdCategoryCode=011005) are some good SCSI hard drives. Just make sure to match the pins on hard drive up with pins on controller card.

As for your SCSI scanner, if you already have a SCSI controller to run it, it may be a good idea to leave it alone and just run 2 controllers. Most new controller cards that support todays really fast drives and other devices don't have external 50 pin connectors. Also, a lot of the SCSI perifereals, such as scanners and CD-RW's, are nor really SCSI. Rather, they are IDE or parallel port, with an adapter. If that's the case, when you run that device it will treat the SCSI bus like an IDE, and only allow one command at a time, thus slowing down your system.

I hope some of this helped.

[kcidwx]

Thanks for the info. I learned a lot and it looks like the Adaptec 2100S might be the best solution for me. I didn't understand what 0,1,2 and 4 channels meant but it appears you can just add more devices 15, 30, and 60 devices.

I assume this card works with LVD and its max transfer is 160mb/s.

I looked at the Adaptec 2110S but I don't think my ASUS board does 64bit/66MHz PCI. I think that's server boards only.

Now I just have to find a hard drive. Does anyone make a DVD+RW SCSI drive?

[jrb420]

Pioneer makes an external SCSI DVD-RW, but unless you REALLY need a SCSI DVD burner I would advise against it. It costs $4500. I know I said I love SCSI stuff, but that's a little much. A good IDE DVD-R would be fine. Since you're going to be burning from a SCSI hard drive, you won't have to worry about buffer underuns and transfer speed. You can buy a good IDE DVD-RW for about $500. HP makes a decent one Still a litle too high for me, but if you've got the cash, go for whichever you want/need. HERE (http://www.circuitcity.com/ewebIMa/detail.jsp?BV_SessionID=@@@@1765299777.1012631073@ @@@&BV_EngineID=ccdeadcefijieemcfngcfkmdffhdffk.0&bookmark=bookmark_0&oid=43561) is an HP model I found on Circuit City's web site.
The Adaptec 2100s is a great card. Same one I plan on buying. It works with LVD. If you go to the Adaptec web site, you'll find a little more info on it. As for hard drives, one of the links I posted should have a good selection. I've heard some people complain about the IBM drives, so you may want to avoid those. Personally, I'm buying 2 Fujitsu 18.6GB 10,000rpm 68 pins for my RAID setup.

[Imperion1]

The ATA100 is the burst speed not the transfer rate. Burst speed is only how fast the hard drive is first accessed and how quickly it spins up. Transfer rate depends on the speed of the hard drive itself. For example: An ATA100 7200 rpm drive will spin up and transfer data quicker than an ATA33 5400rpm drive. Now this might confuse you. An ATA33 7200 rpm drive will spin up slower but transfer data quicker than an ATA100 5400rpm drive.
ATA33 is the slower burst speed.
7200rpm spin is faster than 5400 rpm spin.

Now for SCSI, there is no burst speed (that I know of), but at a 16000rpm spin, the transfer is pretty quick. There are also faster SCSI drives than 16000rpm drives.
And depending on what you are doing would actually depend on whether you should think about SCSI or IDE (ATA drives).
SCSI is more ideal for graphic designers and users. IDE is more ideal (and less expensive) for gamers, internet, and non-graphical apps.