Hard disk format - low level/high level or Bovine

  jack 14:00 27 Jan 03
Locked

Hard disk format- low level/high level - fact or pre-eaten bovine matter?

Some time ago when in difficulty with my hard drive, a man in a repair shop
said "Ah yes sir this is very serious, it has a Trojan virus it needs a " Low level format" with the implication that mere reformatting or even Fdisk and would not be a remedy to the problem [as indeed it had not been] and extracted a large slice of that weeks pension for the privilege.
I have been told since that said individual was having me on - there aint no such thing
as a "Low level format" Fdisk is as low as it gets.
Which is correct?
And if the latter why did repeated formatting not cure the corrupt
operating system installation?

  BrianW 14:05 27 Jan 03

I think you were being fertilised! If you still have the problem try FDSIK /mbr as quite often viruses etc can lurk in the master boot record which is not cleared by a standard FDISK. Then again, there may be others who know better? ;>}}

  jazzypop 14:07 27 Jan 03

click here - FDISK does not format as thoroughly as a low-level format.

  Elrond 15:16 27 Jan 03

There is such a thing as low level format and this is done at the manufacturers factory. It is basically formatted to show the computer it's drive geometry, i.e cylinders heads sectors etc.

  DieSse 16:19 27 Jan 03

Only the manufacturer can do a true low-level format - it's done during the manufacture and CANNOT be changed.

There is a facility called a "zero-fill" - which some manufacturers even (wrongly) call a low-level format. Basically a zero fill resets the HDD back to the state it was in when it left the factory - this does more than fdisk. There are situations that fdisk will not cure.

Most (maybe all) manufacturers have their own zero-fill programs available for free download. The Seagate one is in their Disk Wizard program, for instance. They normally take a mighty long time to run!!

  BrianW 18:58 27 Jan 03

I've learnt something new, which is always good value but to follow up Jack's query - can a Trojan Virus damage a hard disc so badly that it would need low level formatting to be usable? If so, can the damage be undone or is it a case of scrapping the hard disk?
How about an anti-virus programme (AVG6 or the like) could this protect against such a virus or recover a disc after infection?

  DieSse 20:14 27 Jan 03

No - the "zero-fill" utilities will always clean a drive completely.

  Gemma 21:03 27 Jan 03

Please do not confuse the storage device with what can be stored on it. Writing to and reading from a disk is basically easy. Write this string of data to this place on the disk. The data is held in the PC's memory and the place is indicated as sector/track/cylinder. Reading is the reverse. Fetch me the data that is in sector/track/cylinder and put it in this place in memory.

All the sectors/tracks/cylinders are on the disk "out of the box" (including floppies) and cannot be changed without, as DieSse says, sophisticated manufacturing level equipment.
When you buy a new one, the data contained is normally "white space" i.e. binary zeroes.

If a disk has been in use for some time, reformating it does not make it a virgin again. The great majority of the data is still there but the file structure that says where the recipe for fruit cake is stored is removed. That is, the contents table of the disk has been reset. This is a set of data, formally called the Volume Table of Contents, which, by convention, is stored in a default location.

So, as virii are just data (executables and plain data are all the same to a disk), they are written and retrieved just like everything else So, no VTOC, no virus even though it may be there intact after a standard format.

To completely get rid of data it has to be written over. In fact written over many times and in many ways as the little magnetic domains created by the read/write head in the magnetic surface are persistant in many ways. Some of this persistance is due to the very slight mis-alignment of the tracks to the head which gives edge effects, and to other factors which disk manufacturers wished did not exist.

People with really sensitive data on a dead disk use sophisticated methods - they trash it with something heavy.....

  jack 19:59 28 Jan 03

Laptop/which manual/ LowLevel-bovie?

Thank to all for the responses the gen is building fast.
The Manual -Scott Meullers is the one for me
Waterstones are selling it for 25% off great stuff.
Jazzpop the refer for the hard disk is great too.
We are learning.

One more last thing.
This crippled Laptopthingy
The dame appears to have knocked out certain letters
on the keoboard. in particular backslash and M.
whivh means should one wish to type C:\ FORMAT [for example]
you get C: FORAT
Dos does not go a bendle on that as you can imagine.

I have yet to load a Virus killer or run FDISK which may cure it
but what are your reckonings chaps?

  jack 20:01 28 Jan 03

Laptop/which manual/ LowLevel-bovie?

Thank to all for the responses the gen is building fast.
The Manual -Scott Meullers is the one for me
Waterstones are selling it for 25% off great stuff.
Jazzpop the refer for the hard disk is great too.
We are learning.

One more last thing.
This crippled Laptopthingy
The dame appears to have knocked out certain letters
on the keoboard. in particular backslash and M.
whivh means should one wish to type C:\ FORMAT [for example]
you get C: FORAT
Dos does not go a bendle on that as you can imagine.

I have yet to load a Virus killer or run FDISK which may cure it
but what are your reckonings chaps?

  jack 20:02 28 Jan 03

Laptop/which manual/ LowLevel-bovie?

Thank to all for the responses the gen is building fast.
The Manual -Scott Meullers is the one for me
Waterstones are selling it for 25% off great stuff.
Jazzpop the refer for the hard disk is great too.
We are learning.

One more last thing.
This crippled Laptopthingy
The dame appears to have knocked out certain letters
on the keoboard. in particular backslash and M.
whivh means should one wish to type C:\ FORMAT [for example]
you get C: FORAT
Dos does not go a bendle on that as you can imagine.

I have yet to load a Virus killer or run FDISK which may cure it
but what are your reckonings chaps?

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