SCSI vs. IDE

[Bogart101]

Good Day to all!

i just want to raise these questions.
what is the difference between an IDE storage harddrive ans SCSI-3 Ultra3 Wide storage harddrive. can you see these two in a single mobo? can you use it simultaneously, say you have a 40GB IDE HDD and one 9.1GB internal SCSI-3? can you mirror these two?
the only thing i know with SCSI, is that it is much faster than the IDE.
hope these things are clear. http://www.PCGuide.com/ubb/smile.gif

thank you.


[/QUOTE]Their never been a good war nor a bad peace[QUOTE]

[iisbob]

Breifly SCSI is faster, allows " hot swapping " ( long before USB was around ) and can have up to 7 devices on a chain sharing the same channel-whereas IDE is easier to install ( no id's or terminators to set up ), only works with 1 device per channel ( can't have hd on primary master/slave accessed at the same time ) and is now industry standard.

SCSI's just about gone the way of the ISA slot architechture.

You can use a raid setup with either of these two tech's; however you will find that ide is much easier to install/configure. With either an addin card or motherboard that supports it.

Yes you can have a combo of the two-but i've honestly never tried to setup a RAID configuration with them. I would tend to think not however because they use two different types of interfaces.

Let's see if anyone else here maybe has a different possible view on this.


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iisbob

Computer-Show me the Enterprise; no bloody A, no bloody B, and no bloody C-just the original...Mr Scott { from a STNG episode }

[Bogart101]

thanks iisbob!

what do you mean, SCSI requires a card to work? do i have to configure this? what is the largest bytes a SCSI can offer?

[Ghost_Hacker]

I read a article on this same subject.( i think in Maxium PC ) An interesting point was made that back in the day new hard drive technologies emerged on SCSI first, then after a while IDE caught up. So if you wanted to be on the "cutting edge" of hard drive techo. you had to go with SCSI.


Now days that lag time isn't as great as it use to be and in combination with lower cost IDE is slowing replacing SCSI in most workstation enviroments.

[iisbob]

Yes, you need an expansion SCSi card to act as host in order to run SCSI devices ( only motherboards i know of today that support SCSI are server boards )-SCSI U3 transfers around 160MB's per sec if i recall correctly.

Sounds great-until you have to set them up, and keep an eye on them.

And as GH has pointed out, with the advances in EIDE tech, SCSI is now mostly reserved for older server systems, and hobbyists. When the new Serial ATA interface finally gets into the mainstream, you'll see SCSI performance on the ease of IDE type interface.


So i'd advicse you to stick with IDE. If you'd like a little fun tho, try out a SCSI system-it'll keep you busy. http://www.PCGuide.com/ubb/smile.gif



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iisbob

Computer-Show me the Enterprise; no bloody A, no bloody B, and no bloody C-just the original...Mr Scott { from a STNG episode }

[rond36]

To use a SCSI drive you need a PCI SCSI controller card and for mirroring you need one that supports RAID and 2 SCSI HDDs of the same speed and size. The data transfer rate is dependant on the PCI bus because a properly configured ultra SCSI 3 disk array will saturate the PCI bus at 133MB per sec.
Say you have a 40GB IDE HDD and one 9.1GB internal SCSI-3? can you mirror these two? No the drives in a mirror array have to be the same size and speed and on the same RAID channel and controller.
Can you see these two in a single mobo? Yes if you have a SCSI controller installed.
The only thing i know with SCSI, is that it is much faster than the IDE. You may want to check some prices. With the added speed comes the added $$$. An Ultra Wide SCSI 3 RAID controller and 2 15,000 RPM Ultra Wide SCSI 3 36.4GB HDDs will cost about $1,000.00 http://www.PCGuide.com/ubb/eek.gif One other thing with a RAID 1 (mirror) array you may have 2 36.4GB drives but you will only have 36.4GB usable drive space. $27.47 per GB. The same setup using an IDE RAID controller and 2 40GB UDMA 100 HDDs costs about $6.25 per GB. In the real world unless you are working with very large data base files CAD digital video or other data intensive programs you won't be able to tell the difference between SCSI RAID and IDE RAID.

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[Bogart101]

Thank you all for sharing your knowledge.

you need an expansion SCSi card to act as host in order to run SCSI devices ( only motherboards i know of today that support SCSI are server boards )-SCSI U3 transfers around 160MB's per sec if i recall correctly.



iisbob so you mean this scsi drive would be external? i have here an scsi pci card that im using with the scanner. are these card the same?

so as i was reading your replies guys, it seems that it is mush better to use an IDE to save a for myself a hundred bucks and to install the sytem with ease. but im afraid most of the server computer nowadays use scsi.

need some site to enlighten me much about these two drive.

again thank you all.

[Rick]

Most Scsi controllers used with scanners are wide scsi (50pin) a few of these cards have both internal and external device connectors . ( depending of the installed card)


IMHO you wouldn’t want to hook a slow device like a scanner to an Ulta wide scsi 3 controller .
While also using it for High speed devices.
I have always made it a Habit of Using 2 scsi controllers .
One for slower devices (Scanners , cd-rom, zip , and tape drives)
One for the High speed devices Drive storage and raid

Scsi isn’t any more difficult to set up than an IDE drive configuration.

IDE you have primary channel then Master and slave. Secondary Channel Master and slave.
SCSI. You have ID0 (Boot drive) id1,2,3,4,5, and 6 and the terminator jumper on the last device
in full chain that would be id#6 would also have the terminator jumpered..

Limitations of IDE 4 devices across 2 channels
Limitations of Scsi 7 device allowing a mix of internal and external on One controller card.


Setting up a Scsi Raid is no more difficult than setting up an IDE Raid 0 or raid 1

The deciding factor is $$ and or performance

[This message has been edited by Rick (edited 04-20-2002).]

[bassman]

This was one of my favorite topics in school, because when I really understood what the instructor was saying, I imagined a machine sitting on my bench with over a hundred hard drives attached to the wall behind it http://www.PCGuide.com/ubb/biggrin.gif (yes I said over 100 HDs).

Two very interesting points about SCSI3:
1)Up to 16 device IDs per channel (including controler), and up to 7 Logical Unit Numbers per device ID.
2)True Bus Mastering.

Also the fact that no one device on a chain controles the speed of another. So you can have any mix you want (scanner, CD ROM, RAID).

Here (http://www.ahinc.com/scsi.htm) is a link I found that might help with further explination. It does not discuss LUN on this site and I am in a bit of disagreement with how many device IDs you can have, but since I can't verify what I think, I will go with this http://www.PCGuide.com/ubb/wink.gif

As stated by everyone else here, cost is a big issue with SCSI. If you are building a website host server, you want UDMA166 WideSCSI3 15,000RPM setup for 160MBs a second transfer rate. If you just want a really fast desktop computer that doesn't cost as much as a house, go with UDMA133 EIDE 10,000RPM drives and spend the money on a dual processor mobo and RAM.
Good luck http://www.PCGuide.com/ubb/cool.gif

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Waiting patiently for the future to arrive.

Frank's Place (http://dreamwater.net/tech/frankscomp/)

[Rick]

I only see One small flaw in Hooking cd, zip, and Tape drives to an Ultra Scsi 3 controller.
Most if not all of these devices are scsi2 compliant (50Pin) and scsi3 is 68 pin

So Unless you Purchase a Dual connector card ( With both 50 and 68 Pin connectors) you can’t even hook the old slower devises to the controller.

I’m sure there a number of these cards out there today.

[iisbob]

Scsi isn’t any more difficult to set up than an IDE drive configuration.

I disagree, Rick think about it-you only have to set a jumper on IDE drives to either master/slave, no other id's to configure, then just plug it into the ide controller.

On SCSI you have to configure the id's, make sure you have termination, and make sure that the proper drivers are installed. Not to mention you have to watch the pinouts on your peripherals to make sure you have the correct set-either 25/50/68 pins. Ide is standard at 40 pin connectors.

Should you have an id or improper terminatin on a SCSI chain, it can be hell tracking the problem device down-especially in a server enviroment where you literally have dozens' of devices & channels in use.



bassman, i wasn't aware that IDE was up to 10,000 rpms' yet?! Who is making such a speedy EIDE drive?



And yes Bogart101-i menat that the SCSi controllers you see today are internal expansion cards. Most of them have an internal connector for harddrives/CD peripheral's.






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iisbob

Computer-Show me the Enterprise; no bloody A, no bloody B, and no bloody C-just the original...Mr Scott { from a STNG episode }

[Rick]

Bob When you only have 2 drives on a channel yes IDE may be easier ,
BY Exactly 1 Jumper. The terminator
scsi with 2 devices = id 1 and 2 add a 2 pin jumper to terminate

Most every one I know Including Myself.. Clearly Marks each drive installed,
Regardless if it’s scsi or ide
Even A simple pencil mark M-S and or 123 etc and / or As In My case a Logical Order.
Drives numbered Bottom to top 0 to 6 with the tape always being the last device on the chain and terminated.
This even allows for adding additional drives with no worry about termination

I have never been able to understand why people try to make scsi harder than it really is.

If we must compare multiple drive setups above 2 or 4 .
Then look at the new M/B with a built in Raid or additional channels for IDE.
Primary 1 m/s secondary 1 m/s .. Promise controller pri. m/s second m/s
8 drives 8 jumpers .
Under Scsi 7 drives 8 jumpers and only one cable.(possible 2 If I mix wscsi and uwscsi)
And I don’t have to trace the cable back to see where it is hooked up to the M/B
Or have 4 40/80 wire cables to route in the case.

[iisbob]

I have never been able to understand why people try to make scsi harder than it really is.

For PC enthusists/techs like us it's not difficult. But try explaining the simple IDE interface to the average person. Then get into SCSI.

Get the idea!? http://www.PCGuide.com/ubb/biggrin.gif

So that's why i suggest he stay with IDE-not too mention that with Serial ATA we'll see a technology that will offer the ease of IDE with the power of SCSI.



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iisbob

Computer-Show me the Enterprise; no bloody A, no bloody B, and no bloody C-just the original...Mr Scott { from a STNG episode }