Lack of command queueing means that your drive, when issued 10 read commands, may pass over 5 of the sectors it will read in the next few milliseconds to read the first sector requested. Command queueing allows the drive to reorder the read commands, to pull them off the drive in order of which is closest to the current head position. Since, unlike your standard benchmark, your hard disk is constantly moving back and forth between sectors, this makes a big difference. Access time has a much more significant impact on perceived performance than transfer rate does, unless all you do is copy one large file to another drive all day long. Even then, a physical hard disk that's spinning at 7200 RPM has a physical transfer limitation of about 35MB per second, whether it's SCSI or IDE. What's important, then, is to make the best use of each platter revolution. ATA absolutely does not do this. It does provide cheap storage, and the performance can be certainly adequate, but it does not compare with a decent SCSI controller, even in a single drive solution.
No one uses ATA because it's a better performer than SCSI; they all use it because it's cheaper to implement, and easier to configure.
On Wednesday, Jan 14, 2004, at 17:25 US/Pacific, Jesse Stanford wrote:
A good SCSI is comparable to ATA, however in order to get a high-speed scsi bus that IS comparable to ATA you have to buy an add-on card anyway. IMHO, you were using ATA/66 not ATA/133. In order to have a good ata bus you not only have to have the right bus but the right hardware for that bus as well. If you have an ATA/133 drive on an ATA/133 bus it will run fine. An ATA/66 on an ATA/133 bus will drop everything to 66 anyway.<rant>
Ick. While I'll grant that the latest generation of parallel and serial ATA drives are much-improved over the older ATA drives, they still don't compare to a good SCSI bus. If you look beyond published specifications, and actually perform tests, you'll find that command queueing and better bus protocols present in SCSI products make SCSI a much better choice for real-world performance than ATA in a busy multi-tasking machine.
-- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and...
Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! |
Support Low End Mac <http://lowendmac.com/lists/support.html>
PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/>
Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
