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SCSI Hard drives

I have an OEM Adaptec 2940U or 2940UW card.

I want to buy a SCSI hard drive about 9 gigs.  Anyone know any cheap places in Woodland Hills, CA for the best price?

Also can I buy a U2W scsi or even U3 wide SCSI?  I dont know how it works, but I was told if I buy a more powerful drive than my card can take, then it will default to 40 megs/sec.  Is this right?

ALso, does that actually mean I can tranfer data at a rate of 40 megs per second?  I have a UDMA drive at the moment, and I'm supposed to get fast speed.  it sometimes takes me a min to transfer  300/400 megs to another partition.
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oddbod
Asked:
oddbod
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1 Solution
 
oddbodAuthor Commented:
Also how does the 9.1GB BARRACUDA 7200RPM FIBER CHANNEL SCSI 3.5 compare with the 9.1GB ATLAS II 7200RPM ULTRA SCA 80 PIN SCSI 3.5

thx
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Somebody_elseCommented:
whew a lot of stuff to answer, i only know part of it soo...

>I want to buy a SCSI hard drive about 9 gigs.  Anyone know any cheap places in Woodland Hills, CA for the best price

go to:
http://www.pricewatch.com
this web site has the cheapest prices from all over the country.

>ALso, does that actually mean I can tranfer data at a rate of 40 megs per second?  I have a UDMA drive at the moment, and I'm supposed to get fast speed.  it sometimes takes me a min to transfer  300/400 megs to another partition.

when you see 40 M/sec (also Mb/sec) usually with hard drives it means megabit(Mb) not megabyte(MB). The difference is that a byte is made of 8 bits so a megabit is actually 128,000 bytes or 128kb (1,024,000/8 = 128,000).

so if the spec is 40 megabits a second then your transfer rate is only about 5 megabytes a second.

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oddbodAuthor Commented:
Oh ok, I didnt know about the megabit thing.

THx for pricewatch.com already tried that however, just wondering if anyone knows a cheaper price than the £168 quoted on the site :)
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Somebody_elseCommented:
it might be hard to find a cheaper price than on pricewatch, if you are able to find a copy, check out the free publication called Microtimes(usually located at local computer stores, not fry's) this mag has lots of competeting ads for computer hardware.
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Jason_SCommented:
The transfer rates as advertised are maximum, not typical.  Yes, if you buy a faster drive than your controller can handle, it will adjust to the controllers speed.

UDMA is actualy pretty fast.  The gain you get with SCSI is what is called "SCSI disconnect".  An IDE controller will send a command to the IDE device, and wait for a responce back.  With SCSI, it sends the command to the device, then disconnects, and is then free to send another command to another device.  Then it will go back to the first device to continue.  (this all happens in a fraction of a second)  Thus if you have a single SCSI drive, it will not be much if any faster than a single IDE drive.
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oddbodAuthor Commented:
Can you tell me a little more about this disconnect thing.  WHy does the SCSI card have to be setup with different numbers for disconnect?

Nobody has mentioned the different types of SCSI and narror, wide?  Does that refer to the physical size wide or narrow or just the pin size?  Why not make the pin size standard instead of confusing us all!?
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Somebody_elseCommented:
>Nobody has mentioned the different types of SCSI and narror, wide?  Does that refer to the physical size wide or narrow or just the pin size?  Why not make the pin size standard instead of confusing us all!?

pin size (either a wide pin connector or narrow).
they make different sizes to increase the data transfer rate. It started with 40 pin then went to 60 pin(wide) now I think they are up to 80 pin (ultra wide).
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oddbodAuthor Commented:
Do you mean 50 pin and 68 pin?
I think my Adaptec 2940 UW card is 68 pin.  The latest drives have 80 pin I understand.

So is it possible in theory to have a SCSI 3 narrow drive, ie scsi 3 40 pin?
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Jason_SCommented:
UDMA data transfer rate is up to 33 MB/S

SCSI hard drives come in three diffrent configurations.  50 pin, (narrow) 68 pin (wide), and 80 pin.  The 80 pin drive is no diffrent from a 68 pin drive.  It is meant to be used in a configuratin where hot swaping drives is needed.  Both data, and power are passed through this connector.

Here is a rundown on all the diffrent types of SCSI, and SCSI connectors.

SCSI-1 (8-bit Narrow) 5 MB/s 50-pin Centronics (low density).  Standard on older peripherals such as scanners, tape drives, etc.  DB-25 Apple style. Used on products such as the Iomega Zip drive.

SCSI-2, Fast SCSI (8-bit Narrow)  10 MB/s 50-pin High Density. (mini 50, micro 50) Used for peripherals like CD-R and Iomega Jaz drives

Ultra SCSI (8-bit Narrow)  20 MB/s 50-pin High Density. (mini 50, micro 50) Used for peripherals like CD-R and Iomega Jaz drives.

Wide SCSI (16-bit Wide)  20 MB/s 68-pin High Density.  Primarily used for hard drive connections.

Wide Ultra SCSI (16-bit Wide)  40 MB/s 68-pin High Density.  Primarily used for hard drive connections.

Ultra2 SCSI (16-bit Wide)  80 MB/s 68-pin High Density.  Used for hard drive connections.
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oddbodAuthor Commented:
OK thats a good lo-down on the different types.  You forgot to SCSI 3 though?

Can you tell me alittle more about the disconnect feature you talked about, and why different devices need different numbers?
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Jason_SCommented:
SCSI 3 is basically Ultra SCSI.

The SCSI disconnect is basically as I stated.  Using this method, the system does not have to wait for the drive to complete its task before moving on like IDE.

So basically, if you have several UDMA IDE drives running, (at 33 MB/S)

and you have the same number of SCSI drives running, (at 20 MB/S) comparably, the SCSI drives could outperform the IDE drives due to this SCSI Disconnect.

Now that you know more about SCSI that you ever dreamed, my recommendation (if you can afford it) is to get yourself a Ultra2 SCSI controller, with a few Ultra2 SCSI hard drives, and fly like the wind.

And to throw another wrench into the mix, If you get yourself a Ultra2 SCSI hardware Raid card, you could set these multiple drives up as one large drive, and get even better performance out of them.  (4 drives at 80 MB/s = ~320 MB/s theoretically)

It all depends on your needs as to what you end up with.

The different devices all need to have different SCSI ID's so the controller will know which drives to talk to.  Also, be sure to understand, and set the SCSI Termination correctly on the chain.  Auto Termination doesn't mean that you don't have to think about setting the jumpers.
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oddbodAuthor Commented:
I'll be getting my new HD and SCSI CD ROM in a few days time.

I might need your help in setting it up if its not self explanitory.  I doubt they come with instructions.

Shame its not like USB plug and play.  

If its not set properly, it wont blow something will it?  I can handle "incorrect device" warnings or things that make you want to smack it, but dont want to permanently burn something!  - scsi termination
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Jason_SCommented:
If tow devices SCSI ID's are set to the same Id, only one of the devices will be operational.  If the SCSI Termination is set incorrectly, it may still work, but you may loose data, and have other quirky problems.

I'll be around.
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