[Jsnuff1]

Ive heard a lot of arguments in which hard drive type is better, but will please someone give me a straight foward answer in which one os the best.

[Misha]

For performance nothing beats SCSI... esp. Ultra80 and 160... those two fly, and crush ATA. They're pricey, though.

ATA also uses up processor cycles, which makes it less desirable for things like DV.

For most purposes, though, ATA is more than fine. And the price is nice.

Older versions of IDE and ATA (especially PIO mode) did use the processor to direct disk usage resulting in a performance hit, although newer ATA-33, 66 and ATA-100 drives are primarily communicated to via a DMA controller, hence the UltraDMA name.

SCSI drives are nice because they automatically detect surface errors and compensate for problems without end user interaction. The new Ultra 80 and 160 SCSI drives are very nice.

Personally, I love the new ATA-XX drives. They allow me to put nice fast (the new IBM 7200RPM drives are very speedy) and inexpensive disk drives into my systems. I use SCSI drives whenever I need to do something professional and I'm glad Apple still offers SCSI as an option on new Mac's.


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Eliott Wolfe
Winnetka, Calif

I always prefer SCSI, but with the price of ATA now, it's a tough choice. If your just looking for capacity, you can't beat ATA. If it's performance and growth you want, SCSI is the way to go.
With can have two drives, a master and a slave, but you have a performance hit on the slave. SCSI can now support 14 drives per channel.
For single drive configurations, ATA and SCSI are about the same with ATA maybe slightly faster due to overhead in the SCSI protocol However, this all becomes moot when you add a second SCSI drive and set it up in a RAID (the growth part) with SoftRAID or something similar.
A single drive can only pump out so much data and can't saturate the connection (ATA or SCSI). You need to use multiple drives to get the most out of your connection. Thus, don't by an Ultra160 card and connect one drive to it unless you plan on adding more in the future.

Originally posted by Brent:
For single drive configurations, ATA and SCSI are about the same with ATA maybe slightly faster due to overhead in the SCSI protocol However, this all becomes moot when you add a second SCSI drive and set it up in a RAID (the growth part) with SoftRAID or something similar.
A single drive can only pump out so much data and can't saturate the connection (ATA or SCSI). You need to use multiple drives to get the most out of your connection. Thus, don't by an Ultra160 card and connect one drive to it unless you plan on adding more in the future.

Couple corrections here: first, ATA is not faster in a single-drive configuration (assuming similar buses and drives.) The 'maybe' about overhead just isn't there.

Secondly, the multiple-drive issue is an important one. Adding a slave to an ATA bus will kill performance because of master-slave interaction - rather than the controller talking directly to the drive, it goes through the master. This is one reason that you never have software ATA RAIDs with more than 1 drive per bus.

ATA is fine for the vast majority of consumer users. For their usage patterns, it's hard for consumers to tell the performance difference between ATA and SCSI, and it's also much more affordable (which on a certain level is a good thing, too).

However, technically, there is little doubt that SCSI is better overall (albeit more expensive). You have more flexability, faster overall performance/thru-put, and less load on the main CPU. Nowadays, SCSI is mostly used in servers and high-end workstations (such as professional video editing), where every bit of extra performance matters.

I had a whitepaper bookmarked from Quantum Technology (they are a well known hard drive and DLT Tape manufacturer) that explained in detail the performance differences and why SCSI will always be better, but I can't seem to find it at the moment.

-Rick

[Paul Huang]

In situations (such as server applications) where you need to read and write at the same time (as many users are "hitting" the server with different commands), the SCSI wins hands down. SCSI is able to perform multiple read/write at the same time, but ATA isn't.

It's very much like having a UPS delivery truck which only delivers but does not do any pickup. With SCSI, it's like having a truck that picks up and drops off at the same time.

[madcow]

My setup lately have been large ATA drive and a real fast but small SCSI for doing vidios and caching photoshop. I never keep anything on the SCSI.

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Moo

SCSI is better if you're a power user. I owudl know, after you digitize a music video in at 1 GB and hit save you need all the throughput you can get, not to mention when you'r eloading 500MB+ photoshop files.

If you're the average user and dont' need alot of power ATA is okay to go with. If you want performance and reliability go with SCSI.

The main protocal differences (and I actually read a book on this, I'd put in teh ISBN number but dont' want to get this post deleted) in a summary are that with SCSI the computer asks the drive for a specific file/data after that it's up to teh drive as to how it retrives it, just as long as it retrives it. with ATA/IDE/EIDE/DMA/ATAPI the CPU/computer has to sit there and tell the drive 'go to track 300 on platter D and read sectors 34 through 246' sending all of those commands eats up CPU time. Becuase it IS the CPU that acts at the bus controller. On SCSI teh bus controler is a chip all by itself, so even the controlling of the bus is offloaded from the CPU in SCSI.

BTW, if you don't beleive me try formatting a drive in DOS or somethihgn else that really shows you what's going on, or twaek stuff in teh BIOS too, it'll show you all this stuff on sectors and tracks and cylinders.....thats' because teh comptuer actually has to access and know where stuff is on them, the drive doesn't simply fetch it all by itself.

So how do they do it on a mac that uses an IDE/ATA drive? It's rather easy, it goes thorugh all the same crap, they just modified the proprietary chipset/motherboard design to handle ATA and not SCSI, and when you format a drive they just slap a window in tehr eand spin a cursor, thye don't show what's really going on.

Secondly, the multiple-drive issue is an important one. Adding a slave to an ATA bus will kill performance because of master-slave interaction - rather than the controller talking directly to the drive, it goes through the master. This is one reason that you never have software ATA RAIDs with more than 1 drive per bus.

This is absolutely false. The "master" and "slave" labels are just an example of poor naming -- they have virtually identical relationships to the IDE controller. The slave device's data absolutely does NOT travel "through" the master.

Honestly, it's amazing how people will just make this stuff up.

[Dan Szwarc]

You are right! However, regarding the Master and Slave relationship: It is NOT possible to read from one and write to the other at the SAME TIME. The IDE controller can only talk to one drive at a time. The drives have the same priority reagardless of the master/slave status.

For best IDE performance between devices, try to utilize one device per IDE channel. The master/slave on IDE1 can read while the master/slave on IDE2 simultaneously writes. When they are both on the same IDE channel, you take a hit.

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Dan
Michigan Lincoln & Continental Owners Club

[This message has been edited by Dan Szwarc (edited 10-17-2000).]

Would like to do this but have heard issues about the 3 new ATA-66 cards
on older Macs, like my 9600/300. Any recommendations?

Originally posted by madcow:
My setup lately have been large ATA drive and a real fast but small SCSI for doing vidios and caching photoshop. I never keep anything on the SCSI.