topic Interleave factor for SCSI hard drives in Disk

Interleave factor for SCSI hard drives

Andrew Szekely — Thu, 16 Jun 2005 14:33:48 GMT

According to the manufacturer, SEAGATE ST32171WD has an interleave factor 1:1.
When I install this harddive and if I should run mediainit, what should I enter as an answer?
Thanks for your answer, Andy

Re: Interleave factor for SCSI hard drives

Suraj Singh_1 — Fri, 17 Jun 2005 00:00:13 GMT

Hi Andrew,

Go through the following link before trying mediainit with -i option.

http://www.storagereview.com/guide2000/ref/hdd/geom/tracksInterleaving.html

Extracts from this site:

"So this begs the question then: how do you know what interleave factor to use? Well, on older hard disks, the interleave factor was one parameter that had to be tinkered with to maximize performance. Setting it too conservatively caused the drive to not live up to its maximum potential, but setting it too aggressively could result in severe performance hits due to extra revolutions being needed. The perfect interleave setting depended on the speeds of the hard disk, the controller, and the system. Special utilities were written to allow the analysis of the hard disk and controller, and would help determine the optimal interleave setting. The interleave setting would be used when the drive was low-level formatted, to set up the sector locations for each track.

On modern disk drives, the interleave setting is always 1:1. Controller too slow? Ha! Today's controllers are so fast, much of the time they sit around waiting for the platters, tapping their virtual fingers. How did this situation come to change so drastically in 15 years? Well, it's pretty simple. The spindle speed of a hard disk has increased from 3,600 RPM on the first hard disks, to today's standards of 5,400 to 10,000 RPM. An increase in speed of 50% to 177%. The faster spindle speed means that much less time for the controller to be ready before the next physical sector comes under the head. However, look at what processing power has done in the same time frame: CPUs have gone from 4.77 MHz speeds to the environs of 1 GHz; an increase of over 20,000%! The speed of other chips in the PC and its peripherals have similarly gotten faster by many multiples."

Bottom line: DO NOT USE -i OPTION IF AT ALL YOU WANT TO USE mediainit

~Suraj

Re: Interleave factor for SCSI hard drives

Uwe Zessin — Fri, 17 Jun 2005 00:15:19 GMT

Today's systems operate on logical block ranges. The cylinder/head/sector values are a legacy.

For many years, disk drives do not have a constant number of sectors on all cylinders. The outer ones have a larger circumference, so they can put more data on them while retaining the same write density. The CHS value which a disk drive reports is fake!

Re: Interleave factor for SCSI hard drives

Alexander M. Ermes — Fri, 17 Jun 2005 05:18:00 GMT

Hi there.
That is a shadow from the past decades ago.
Don't change it. An interleave factor of 1:1
is the best you can get anyway. The meaning of the interlave factor was that the head of the disk had to move over a certain number of blocks on the the disk, before it could read the next one. The internal geometrie of disks has changed so much, that there is no real need to care about it.
Rgds
Alexander M. Ermes
p.s.
controlers to use this were the old WD1003 MFM or similar things.