Forum OpenACS Q&A: Off Topic: head/sector/cylinder on hard-drives

Collapse
1: Off Topic: head/sector/cylinder on hard-drives
Posted by Ola Hansson on 07/22/01 06:34 PM
I want to run IDE Raid 1 on my new OpenACS server, so I went out and
bought a computer with three IBM Deskstar 75GXP 75GB drives (one for
backups) and a Microstar K7T266 Pro motherboard. The mobo has two
extra IDE channels with Promise "Lite" IDE Raid. After fooling around
for a while I decided that I'd use Linux software Raid instead...

Now, when I install RedHat 7.1 and use "Disk Druid" to partition the
disks I find that the head/sector/cylinder settings have been altered
by the Promise Raid. The original configuration was; 16/63/148945 but
is now; 255/63/9345. The size of the disks haven't changed much
though. When I try to change back to the original values using Fdisk I
find that the largest value for cylinders is 131071 or something. So I
must increase the number of heads to keep the full size of the drive.

The question is: What impact does different settings of
head/sector/cylinder have on performance and so on?

Maybe you know where I can read about it?

Thanks,

Collapse
2: Response to Off Topic: head/sector/cylinder on hard-drives (response to 1)
Posted by Rodger Donaldson on 07/23/01 06:11 AM
None, in practise.  CHS settings are basically a fiction of the PC architecture, and drives can (and do) return made up numbers to the BIOS - and different BIOSes may return different numbers (which is probably why you're seeing them change across different IDE controllers).
Collapse
3: Response to Off Topic: head/sector/cylinder on hard-drives (response to 1)
Posted by Jonathan Marsden on 07/25/01 11:58 AM
One EIDE FAQ is at http://thef-nym.sci.kun.nl/cgi-pieterh/atazip/atafq.html and the more technical stuff from Hale Landis is at http://ata-atapi.com/hiw.htm, with his document about CHS stuff specifically being at http://ata-atapi.com/hiwchs.htm