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Reformatting drives to refresh the format

I don't think I've heard any mention of "low level format" in many a year now, but there was a time when that phrase was tossed around loosely and inaccurately.

This old post spelled out the reality of disk design and is interesting in a historical context.

This reminded me of another utility from that era - Gibson Research Spinrite. Hard drives have become so reliable that I was really surprised to see that Spinrite still sells that product! Their FAQ page has this note:

No software of any sort can truly low-level format today's modern drives. The ability to low-level format hard drives was lost back in the early 1990's when disc surfaces began incorporating factory written "embedded servo data". If you have a very old drive that can truly be low-level reformatted, SpinRite v5.0 will do that for you (which all v6.0 owners are welcome to download and run anytime). But this is only possible on very old non-servo based MFM and RLL drives with capacities up to a few hundred megabytes.

I hope no one does still have those drives!

Newsgroups: comp.unix.sco.misc
From: bill@bilver.magicnet.netREMOVETHIS (Bill Vermillion)
Subject: Re: How do I low-level-format an IDE Drive?
Message-ID: <F9xI4w.1sFB@bilver.magicnet.netREMOVETHIS> 
Date: Fri, 9 Apr 1999 15:38:56 GMT

In article <370C994A.C3D561BC@ilion.nl>, Tony Earnshaw
<tonye@ilion.nl> wrote:

>Frank Overstreet wrote:

>> ... Now I want to low level format the drive and am wondering
>> if the Western Digital utility wddiag.exe is what I need. When
>> the readme describes writing all 00's is that the same as a
>> low-level-format. If not please help.

>If you even attempt to low-level format a modern IDE disk, you'll ruin
>it. This has long been the case. Writing all 00s is not the same as a
>low-level format, it's what it says.

>Low level formatting was possible, after manufacture, with (now) almost
>prehistoric drives to remagnetize surfaces (thereby removing corruption
>and thus sometimes repairing some bad spots on the surfaces). These
>drives did not carry translation tables, as modern drives do.

The old wives tale of 'remagnetizing' the drives is just a myth.
Magnetic media is quite stable - it's the environment that does
them in re-acting with binders in coated media.  Media for the most
part is plated/sputtered today, so the only problem is the decaying
of the particles.  It just doesn't happen - at least in a computers
lifetime.  This excludes catastophic events of course, and high
heat levels - above 150F you are going to have problems.

One of the ways the myth seemed to get started was on the old MFM
drives of the ST-506 heritage.  These were all 'stepper' drives.
eg - a motor turned x degrees and ratchets the head across the
drive surface.  (In the floppy arena it was typically to have
to re-aline a 5.25" disk every 6 months when used in heavy duty
service.  I did that but was pushing them 24x7x365.  The first
drives would last about a year, and when the 1/2 heights came out
you could expect 4 years approximately - MTBF was about 20,000
hours for those).

The mechanism would wear over time and when the drive was issued
commands to pulse/step the drive to the track, after a time it
the head would not be positioned exactly in the center of the track
set by the original format, and a reformat would then bring back
the performance as first seen as the platter to stepper were now in
sync with the worn portions.

To try to improve performance embedded servos were being used.
This was a servo burst in between sectors.  Doing a real low-level
format meant the drive had to go back to the factor for a new
format and servo.  It was expensive.  Typically the servo looked
like a 'wedge' if you viewed it magnetically as the outer tracks
had the bits spread further apart.

Then came the dedicated servo drive - with the bottom platter
being used only for servo.  This is why you'd see drives
with and even number of platters, but one less than the total
for data.

These are the drives that perform the thermal recal because as the
enivornment changes the metals contract and expand and the bottom
head is controlling the position of all other heads on the stalk.

Current technolgy is embeded servo again - but there's no way a
user can screw these up - as the old drives were controlled by
cards external to the drive, and the new ones are integral to the
units.

This eleminated thermal recallibration, ZBR (zone bit recording)
gives a different number of sectors available on different track
groups.

Low-level reformating really needs never to be done.  Worst case -
to get rid of some pesky droppings by some ill-behaved program, or
programming concept, would be the destructive verify in the
controller.

But 'reformatting to refresh the format' is something left over
from DOS circa 1985.

-- 
Bill Vermillion   bv @ wjv.com 

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