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i want to buy one hard disk for my system some body saying that scsi is good but the cost difference between ide & scsi more

Posted on 2003-03-16
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i want to know  what is the main difference between ultra2 scsi drive & ATA100 hdd drive

pls tellme about this
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Question by:thotadurga
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by:
hoodrider earned 100 total points
ID: 8149619
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Assisted Solution

by:BigSchmuh
BigSchmuh earned 100 total points
ID: 8151336
I read hoodrider's url and think some comments may be added:
1/ CPU resource difference
Using IDE will make your CPU do the job instead of letting the Disk controller do it.
==> This is not an obvious impact to plan on and you should expect as high as a 20-40% CPU consumption if you have very intensive IO operation on your IDE drives...

2/ Hard drive speed and numbers
You will easily find IDE drives up to 10000 rotations per seconds but SCSI drives rotates up to 17500 which means they are able to deliver almost 75% more datas in the same period...
Be aware that usually you can not have more than 4 IDE drives (including your CD reader!!!) which does not give you many options...

3/ Security
I agree with hoodrider's url on this topic (Hot swap-hot plugs are not available on IDE to my knowledge)

==> If you do not need production performance for a database or IO intensive app and do have some CPU extra resource, you can surely go to an IDE disk subsystem.
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Expert Comment

by:SunBow
ID: 8154027
supplementing, IDE gives 2 drives per primary and secondary, while scsi provides seven devices to start with. So you can easily make a system with a separate mass storage device for each letter of alphabet.

SCSI is more expensive, because fewer are produced. To provide them an ID, you must assign an individual number from 0-7. For IDE you have to assign separately master/ slave/ cable sense - for each ribbon cable, and the actual position on the cable can influence its ID.

Seven scsi drives are easily daisy-chained on single cable. For IDE you get two. Including CD.

Scsi has a separate transfer mode called synchronous, permitting speed increase of tenfold for bursty traffic.

Scsi requires a separate controller device. Most computers do not have that expense ticket for IDE. This gives SCSI user a chance to run SCSI BIOS utilities, such as reconfiguring boot order, fine-tuning speed, performing low-level formats or simple disk scanning validations/verifications, etc.

IDE requires one drive as master, prestrapped so, for SCSI the first HD is usually #'d as 0, but it can be 1, or 2, etc. no fixed necessity there.

You might check out the Adatpec website. They've invested a good deal in scsi, so they should be a good resource.
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Expert Comment

by:pbarrette
ID: 8154531
Hi all,

The big downer to SCSI is the price. A typical 80GB IDE drive will run about $100 US whereas a typical SCSI 73.4GB drive will cost $400 US minimum.

I think BigSchmuh is mistaken about the CPU utilization of IDE vs. SCSI. You may want to have a look here for more info and a direct drive comparison:
http://storagereview.com/welcome.pl/http://storagereview.com/articles/9807/980706seamed9.html

Also, products do exist that allow the hot-swapping of standard IDE drives:
http://www.whiningdog.net/Reviews/PC/Accessories/Cases/20021223-ISWAP4/

This will likely become a moot point soon, since the new Serial ATA drives and controllers have native hot-swap support.

pb
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Expert Comment

by:dew_associates
ID: 8155902
thotadurga, the principle difference between SCSI and IDE is the ability to go beyond the 4-device limitation imposed by the IDE:0 and IDE:1 bus. Most top of the line SCSI controller cards permit as many as 14 devices, one of which is the controller itself. There are benefits and pro and con today to both that weren't present just a few years ago. The main reason for SCSI drives over IDE several years ago was generally they were larger in capacity, faster and with the use of the NTFS file system, you didn't have the limitations imposed by the FAT files system. By using a good SCSI controller you you create one or more volumes composed of several SCSI drives, which could not be accomplished with IDE. In addition, RAID and Mirro configurations were not available to IDE as they were to SCSI interfaces.

The links provided by others provide some reasonable historical information about drive configurations, but for the most part all of them are terribly outdated. At present, SCSI is still the best, and the price point has dropped substantially. One issue used to be the ability to hot swap SCSI drives in mirrored or RAID configurations, but this too is now avalable to IDE, and will become even more flexible as soon as serial ATA becomes more available.

The next step towards improvement will be the eminiation of the motherboard BIOS as the controlling code for your system. It is expected that the BIOS, as we know it, will be eliminated within the next 18-24 months.

Dennis
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Expert Comment

by:LucF
ID: 10303848
thotadurga,
No comment has been added lately (327 days), so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area for this question:

RECOMMENDATION: split points between hoodrider http:#8149619 and BigSchmuh http:#8151336

Please leave any comments here within 4 days.

-- Please DO NOT accept this comment as an answer ! --

Thanks,

LucF
EE Cleanup Volunteer
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Expert Comment

by:dew_associates
ID: 10306563
I disagree LufF. As a matter of fact, both of your suggested respondents did nothing more than offer outdated information, and even at that at least one comment was an assumption, that because a drive spins 17,500 as opposed to 10,000 RPM (not seconds) it will deliver 75% more data. Seriously, you perceive that as an answer? At least Sunbow and I provided current information that also happened to be recent.
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by:BigSchmuh
ID: 10307900
dew_associates: I read again those posts and I do not see where you can claim such "Outdated" info. I even mention that Hotplug (and I maintain that the drive speed is the key to data delivery speed)...so please cool down
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by:pbarrette
ID: 10307978
Hi all,

Just wanted to clarify some things.

1. Higher rotation speed does not mean greater data throughput. It does, however, minimize the "seek" time. That is the time it takes for the HD to locate non-contiguous data on the drive. Data throughput is limited by the drive interface specification and the computer's system bus.

2. Hotswapping is available for non-serial ATA, IDE drives. Just look on google for "mobile rack" and you will find plenty that support hot swapping. In addition, not all SCSI drives and devices are hot swappable. You must have a hot-swap backplane for the SCSI devices that you wish to hotswap.

3. The drive electronics in IDE drives are almost exactly the same as the drive electronics in SCSI drives. The differences between the two are largely due to the specifications themselves and the communications protocols.

4. SCSI is still extremely expensive in comparison to IDE. That much, at least, is not outdated.

5. This is a 50 point question. (Just a reminder)

pb
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Expert Comment

by:LucF
ID: 10308057
dew_associates,
I understand your consern, and I have to admit I only glanced the link from hoodrider wich looked very promising to me. In the comment BigSchmuh the only thing I saw to be faulty what exactly what you pointed out. I've seen too many problems with hot-swappable IDE casings to trust them. Nowadays with SATA this is not an issue anymore.

Still open for suggestions how to split the 50 points.

Greetings,

LucF
EE Cleanup Volunteer
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Expert Comment

by:SunBow
ID: 10311710
I like scsi. I like pbarrette's last comment. I suppose I could also be partial to a SunBow. It'd be nicer if thotadurga would give feedback, and not be a single question user of low bid.  More often, a newbie would give 125 points for such a question if really interested.
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Expert Comment

by:dew_associates
ID: 10312422
The information provided by hoodrider, at the time this question was asked, was over three years old, and has since been updated, October 2003, or seven months "after" this question was asked. Now, as for BigSchmuh's comments (and there's no reason to cool down as I'm not heated up) first, as it pertains to CPU utilization, while there is an impact on the CPU, it's no where near 20-40% today. That close to being the case 3-4 years ago, but with the release of the 7xxx and 8xxx chipsets on the ID controllers, even some released by IBM, the impact, even at sustained disk reads/writes is less than 8-10%. Second, higher disk rotations as they pertain to read/write access is negligible at best. In real world situations, disk fragmentation creates a greater impact than rotational speed. Additionally, when you throw spanned volumes into the mix, rotational speeds as they pertain to read/write operations today are barely noticeable. Third, security and hot swappable drives are two different subjects. Hot swappable IDE drives were available in 2002.

My recommendation would be a split between pbarrette, sunbow and myself.
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by:pbarrette
ID: 10312648
Hi all,

I'll opt out of this one. Thanks.

pb
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by:LucF
ID: 10312695
>>My recommendation would be a split between pbarrette, sunbow and myself.
50 points can't be split three ways.

Sorry, but I'm going to leave this one for the Mods if you don't mind. I hope thotadurga will give some feedback.
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Expert Comment

by:BigSchmuh
ID: 10312817
I learned many thinks on hd drives along those posts (but I was the first to claim about ide cpu consumption).
Well, if you offer me 2 points, I will allow a nice 16 points repartitions to all of you 3...ah...ah...ah
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Expert Comment

by:dew_associates
ID: 10348841
Force accepted by someone that doesn't have a clue on the advice os someone with even less of a clue. And you people wonder why the PAQ is nothing but trash?!?!?
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by:dew_associates
ID: 10366353
I did respond because I do care, but when speed replaces quality, it really doesn't matter anymore. All this does is fill the PAQ with misinformation which reduces site integrity. Unfortunately we are being reduce to just another message board with more and more imput from the unknowing.
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Expert Comment

by:dew_associates
ID: 10387031
Well let's see if we can take it from the top shall we? Most of the cleanup volunteers are just that volunteers, which implies nothing as to credentials. Indeed, the information is auctually more than a year old, especially considering the changes and advances the last tweo quarters of 2003. Do I expect moderators to be experts in every TA?, no I don't, but I do expect them to look to their lead experts, and when there is a question about the veracity of information, I expect it to be checked. Lastly, while indeed you may lead me in this area, I lead you overall and have the credentials to back it up. Leading in "storage" really doesn't mean much if the technology and software used to implement the device is not understood as well.
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Expert Comment

by:dew_associates
ID: 10387899
I agree, I don't want to get into a contest either, but we either put good information in the PAQ or none at all. In my opinion the selected answers to not respond to the question in current techonology. Therefore, if someone reads this question tomorrow, aside from the misinformation, then it has no value. The reason is simple really, the question was: i want to know  what is the main difference between ultra2 scsi drive & ATA100 hdd drive. While the referenced link is good, it does nothing for the pack as the PAQ relies on a link that's here today and gone tomorrow. More importantly, even though Mike updated his information, it is still inaccurate as there have been defined dedicated drivers for NT based systems since the release of the 7000 series chipsets almost 5 years ago.
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by:pbarrette
ID: 10388086
Hi all,

Unfortunately, I am still subscribed to this thread and have been watching it all unfold.

That being said, I still hold that the main difference between Ultra2 and ATA100 is the massive price difference.

Anyway..

The question was badly formed and open ended from the beginning. The user didn't address any specific questions he may have had, nor did he respond to his own question in any way. The question is just as invalid as "What's the difference between Windows and Linux?" You could argue either one all day long and still get nowhere.

Furthermore, the validity of this as a PAQ'ed question is totally shot now that several experts are having an argument over the correct disposal of the 50 points at hand. I feel that any disputes should be handled via email to the admins or in the "Community Support" TA so as not to clutter the actual topic with these types of arguments.

In my opinion, this whole thread should be deleted, or all posts from LucF's on down removed. Dew's post stating that the information provided is outdated is still a part of the thread.

Anyone using information found on the web for critical applications would be wise to double check their sources anyway.  Anyone who doesn't read the entirety of the posted information deserves what they get as well. Most of the PAQ's on EE are created by the question asker accepting an answer. That is, the person who didn't know to begin with is assigned the task of selecting the best answer. I've been in several questions where the asker chose a wholly inappropriate answer as correct. Do we now go through all of those and debate with the moderators as to which is "really" the best info for the PAQ? No, of course not.

Just my $0.02 (US, before taxes) as always,
pb
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by:SunBow
ID: 10637942
Status?
I agree with dew_associates  Date: 02/08/2004> I disagree LufF. As a matter of fact, both of your suggested respondents did nothing more than offer outdated information, and even at that at least one comment was an assumption, that because a drive spins 17,500 as opposed to 10,000 RPM (not seconds) it will deliver 75% more data. Seriously, you perceive that as an answer? At least Sunbow and I provided current information that also happened to be recent.  

except on the latter, the extra scsi HD capability is old news and the higher speeds are more recent news, but I agree that rotational speed is not much value (although drives for both IDE and SCSI eventually are made for approx. common size in GS and speed in rotations). RPM value does not follow a flat line graph in simple algebra.

My own PAQ beliefs are to never delete if one can help it, more is better concerning information, and concerning this particular one, there are numerous comments that if taken together, can assist a PAQ researcher in determining truth as well or better than numerous 500 pt PAQs. For the few points offered, I don't think we should dwell on it too much, outside of adding some general compliments and thank yous to mods and cleanup crews, including LucF, and one more remark

LucF> Nowadays with SATA this is not an issue anymore.

My first (old) scsi could handle seven HDs on a single ribbon. My SATA can do two HD, and cannot use well old IDE ribbon, and I need to create more diskettes on hand to get it to boot.

pbarrette> 4. SCSI is still extremely expensive in comparison to IDE. That much, at least, is not outdated.

Not exactly. It is a little more expensive, just more extreme for first production runs of the models.  Main reason is less the technology, than the quantities manufactured, with the off-shelf models defaulting to supplying IDE.


I vote for PAQ as-is, no delete, no refund, and won't take any more time to think about what to do about moving the few points around this way or that (deferring to others above)
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by:pbarrette
ID: 10641296
Hi SunBow,

Wow.. I can't believe the discussion on this one is still going.

Anyway, I still stand by my statement that SCSI is extremely expensive when compared to IDE.

For comparison:
Controller = Adaptec 39320D Ultra320 SCSI
Drive = Seagate ST373307LW - 73.4 GB - 10000 RPM
Max Theoretical throughput = 320Mb/s
HDTach 2.61 Reported Avg. throughput = 55.2Mb/s Read - 35.1Mb/s Write

Controller = Iwill WO2-R Motherboard with American Megatrends HG80649 ATA100 controller
Drive = Western Digital WD1200JB - 120 GB - 7200 RPM
Max Theoretical throughput = 100Mb/s
HDTach 2.61 Reported Avg. throughput = 38.2Mb/s Read - 24.7Mb/s Write

Costs:
SCSI Controller - Adaptec 39320D = ~$250 US
IDE Controller - Built into all Motherboards = Free.

SCSI Drive - Seagate ST373307LW = ~$350 US
IDE Drive - Western Digital WD1200JB = ~$105 US

So:
Total cost of IDE = ~$105 US
Total cost of SCSI = ~$600 US

In SCSI's favor - ~30% faster
In IDE's favor - ~200% more storage capacity - ~85% cheaper

I'd say SCSI is "extremely expensive in comparison to IDE."

pb
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by:Axter
ID: 11507984
Just to add my 2 cents,
I'm glad this question was not deleted.

In doing a keyword search for "SCSI VS IDE", this question turned up on top of the list.

I was easily able to skip the first few comments, including accepted answer/assist, and went directly to pbarrette's link.

The first three comments were mostly regurgitated information that I've heard before, and when reading pbarrette's comment I could easily tell he/she had the information I was looking for.

I recommend not deleting this question.
I also recommend reopening the question, and setting it to zero points with out awarding it to a particular expert.

IMHO, the currently accepted answer/assist is misleading at best.

I also recommend deleting the quarrelling  comments.
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