a modest request

[Alan Cox]

On Fri, Dec 17, 2004 at 10:05:15AM -0500, gslink wrote:
> The problem with bad sectors is not with sectors that show a write check 
> but with those that don't show a write check but are bad.  The write 

There is no way to detect disk errors of this form. Nor do we need to 
because the drive will do sparing for us

> check on most hard drives is very simple and consists only of parity. 

Wrong. The check on any modern drive is built around very complex mathematics
because the bit density is so high that the data is always full of errors.
Advanced FEC algorithms are used which can not only analyse the data and
recover it from the noise but also assess how close to unreadable the block
is and can then rewrite the block and if that fails move it.  IDE disks also 
pretty much ignore "format" and "verify" commands except for reading each disk
sector and checking if it seems acceptable.

If most of the disks you get have bad spots find a proper supplier. I've only
seen that occur when people are not shipping drives properly (so the get 
damaged in transit) or if the vendor is recycling RMA'd drive pulls on the
quiet.

Out of the box drives don't come with errors and haven't seen the days of
EIDE.

Alan