UDMA4

[Thomas Ratliff]

-----Original Message-----
From: Brian Arsenault <barsenault at gto.net>
Sent: Feb 26, 2004 10:27 PM
To: fedora-list at redhat.com
Subject: UDMA4

>Hello,
>
>Just wondering if anyone has any tips for enabling UDMA5.

Don't really have tips, but I can share my experiences

I've tried extensively with hdparm on a couple drives and the conclusion I came to is that unless you really know what you're doing, you should probably leave the defaults. When I've been able to get a drive to work in UDMA5, I tend to get lockups and crashes. Testing with hdparm -Tt I see minimal improvement (if any) in the higher modes. 

My new Hitachi 80 Gig drive will do about 33 Megs/second sustained transfer rate (under Windows and Linux). This means UltraATA 66 is nearly double the bandwidth this drive needs. The only time you want or need performance beyond UDMA 66 is if you've got 2 fast drives that are often transmitting over the bus at the same time, and maxing out that 66 megs a second. This generally only happens in servers, and you'd be using RAID or SCSI drives for that anyway. 

In short: you're probably not missing anything except performance you will never use anyway. Save yourself the headaches, and use the defaults.