🚀 go-pugleaf

Ian Staples <ianst@refer.to.sig.au.invalid> wrote in
message news:8q78tu$3m1$2@bunyip.cc.uq.edu.au...
> phaywood@alphalink.com.au.REMOVE.THIS.BIT wrote:
>> Steen Nielsen wrote

>>> Hi I need a dos program to repaer bad sectores on my harddrive
>>> can any one please tell me which program i should use.

>> You can't fix bad sectors. They're a fact of life.
>> There's really nothing you can do. Those sectors
>> have gone to the great bit bucket in the sky.

> Is everything so clearly black or white,
> or can we have a bit of grey here too?

If you insist, even a cane toad can have some grey.

> Up until 72 hours ago I may have unconditionally agreed with
> the "great bit bucket" concept, but I'm now wondering about it...

Its just plain wrong stated as absolutely as that.

It really depends on what produced what appears to be bad sectors.
It is possible for some software to decide that a particular sector is
bad at the OS level and just mark it as bad at the OS level, in the
FAT. That can happen not because there is a problem at the level
of the media layer on the platter but just due to errors higher in the
chain so the software sees what appears to be a bad sector but
which is fine at the level of the sector on the media.

Those can obviously be fixed just by a format at the OS level.

Even when a sector has gone bad on the physical platter, most
modern drives do have what is often called a low level formatter
but which in fact is just a ute which scans for and adds new bad
sectors to the bad sector list and makes the drive appear to be
error free. Clearly in that case the bad sector hasnt actually been
repaired, only mapped away, but thats the least common reason
for bad sectors because the original bad sector scan done at
manufacturing time is done at reduced signal levels to detect areas
where the media isnt good enough and that doesnt change over time.

You can however sometimes get at bad sector due
to a power glitch while the sector is being written.

And in the ultimate his statement is wrong with drives where
you can do a true low level format which rewrites the tracks.
Thats not that common at all anymore with embedded servo
drives but was very common with the earlier stepper motor
drives that got a phenomenon called sector jitter due to thermal
effects. A low level format would certainly fix bad sectors with them.

> You see, a bloke who clearly knows more than I do about such
> things in general (he's a PC support professional) recently told
> me that  one of the ways some modern demo programs "know"
> whether they've been installed previously is to mark a sector bad.

Yeah, thats been used for many years. Strictly speaking
thats not a bad sector tho, just one thats been marked bad.

> [And, presumably, put a bit of stuff in that sector to
> confirm that they've done it when they look again later?]

Can be done that way or just keep track of
where that phantom bad sector is on the drive.

> If this is so, then maybe there would be a way to recover such lost space?

Yep, in that case just an OS level format will do it.

> Whether it would be worth the effort is another issue
> -- I guess it depends whether this scenario is real;
> and, if so, how many demos you trial. ;-)

You can get a situation where there is some problem in the
hard drive subsystem that sees lots of sectors marked as bad
at the OS level, say when you run scandisk etc. Once you fix
the cause of those bad sectors, an OS level format will recover
what has been marked as bad but which arent in fact bad at all.