What is Low Level Formatting

[lord loh]

In the Post,

http://www.codeguru.com/forum/showthread.php?s=&threadid=227798

Cakkie, Super Moderator
Said:
...a low level format isn't something you should do to format a disk. A low level format is a very dangerous thing to do if you don't know what exactly you are doing. It will recreate tracks and sectors on the HD surface. Each HD can only adapt to specific settings (these are typically on a label on the HD itself), if you use other settings, you could wind up with a unusable HD.

So what really happens ?
new tracks and sectors are created...So what is the problem ?
And what are these 'specific HD Settings' ?
Does this have any thing to do with the cluster size...


Thank You

[Andreas Masur]

Low-Level and High-Level Formatting (http://www.pcguide.com/ref/fdd/mediaFormatting-c.html)...

[mwilliamson]

High level formatting rewrites the fat and boot sector, then verifies every bytes on the drive is readable. Low-level formatting writes 0s across the entire drive. Generally it is a bad idea to lowlevel format. Sometimes it is difficult to make the disk usable again. And of course there are many people who say it will make your hard drive slower.

[lord loh]

According to the article given indicated by Andreas Masur, I understand that, when HDs are made, they are blank(nosectors,no tracks,no File Syatems).
Then a low level format is done by the manufacturer.

from that article...

There are two steps involved in formatting magnetic media such as floppy disks and hard disks. The first step involves the creation of the actual structures on the surface of the media that are used to hold the data. This means recording the tracks and marking the start of each sector on each track. This is called low-level formatting, and sometimes is called "true formatting" since it is actually recording the format that will be used to store information on the disk


==>Is this format "generic" or is specific to DOS/WIN/MAC/Linux ?

And after the lowlevel formatting, a highlevel formatting is done which creates a logical structure and File system root directory etc..

==>If 0s are written through out, what is the trouble ?

==>Why should the disk become unusable? And Slow down ?

==>And under what circumstances is low level formatting recomended?

Thank You for replying!
My Gratitude...

[TheCPUWizard]

When a "low-level" format is being done, it is to write the initial sector and track information as previously described. This is a physically dangerous [to the disk drive] operation and may easily result in permanent destruction to the drive

That said, now the question is why is this so.....

Since this type of formatting is done without there being any information on the drive for the Servo loops, the mechanics of the drive must run in a semi-open loop. This can cause over or under travel of the head assembly.

In the old days of MFM and RLL drives (precursors to IDE drives), the densities were orders of magnitude lower and the heads physically much larger. Small errors in travel were not not typically a problem.

As the densities have increased, each manufacturer has taken their own internal approach to achieving the required tighting of tolerance and has developed their own method (including hardware) for doing the required low level formatting. This effectively means that a generic low level formatting routine is no longer practical (possible?).

Some vendors (notable Maxtor) provide their own low level formatting software (MaxBlast). Others do not. Most of these now check the model number of the drive to make sure it is safe to attempt the low level format. However some do not.

In conclusion, the only time a low level format can be recommended (as a generalization) is when the drive is totally un-readable, is not under warrentee, and you have a version of the software for that specific drive type. In all other cases it is suggested that you contact the manufacturer for instructions directly. Unless of course you are willing to take the risk of destroying a drive (it's kind of fun to open one up after destruction to see how thay actually work...)

[mwilliamson]

I don't know why low-level formatting would make a drive slower... maybe cause the manufacturer optimizes part of the drive that is overwritten? I really don't know, it never made sense to me. But I know many people who beleive it, and have seen pretty graphs and such to show it :) If you search google, you should come up with something.