Bad Block

  • Thread starter Thread starter guru.naveen
  • Start date Start date
G

guru.naveen

Hi,

How the Scan utilities detect Bad Blocks. On what Criteria, it will
tell that particular block is a bad block.

Thanks

Guru
 
Hi,

How the Scan utilities detect Bad Blocks. On what Criteria, it will
tell that particular block is a bad block.

Thanks

Guru
Click to expand...

A block is bad when the disk subsystem is unable to
read a cluster. Run chkdsk /f /r from the Command Prompt.
 
I think is both write and read.


Pegasus (MVP) said:
A block is bad when the disk subsystem is unable to
read a cluster. Run chkdsk /f /r from the Command Prompt.
Click to expand...
 
hi,

also what I want is what exactly mean ' unable to read' -

How it will decide that it is not able to read.

Whether it will -- cross check with previously written ECC with the
currently existing data.
if it doesn't match then it is read error or bad block ??

Regards

Guru
 
guru said:
Whether it will -- cross check with previously written ECC with the
currently existing data.
if it doesn't match then it is read error or bad block ??
Click to expand...

Hi

Google for 'ATA command set' to learn what disks themselves do before a
read/write error is reported. Indeed ECC is one means of verifying and even
correcting data.
 
guru said:
hi,

also what I want is what exactly mean ' unable to read' -

How it will decide that it is not able to read.

Whether it will -- cross check with previously written ECC with the
currently existing data.
if it doesn't match then it is read error or bad block ??

Regards

Guru
Click to expand...

All data read from memory or from bulk storage medium
goes through a CRC check (Cyclic Redundancy Check).
This check allows the operating system to detect read
errors in much the same way as you can detect spelling
errors in an English word. It is also possible that the read
head does not get a "0" or "1" of sufficient signal strength.
 
Pegasus (MVP) said:
All data read from memory or from bulk storage medium
goes through a CRC check (Cyclic Redundancy Check).
Click to expand...

It's a tad more complicated than that.
This check allows the operating system to detect read
errors in much the same way as you can detect spelling
errors in an English word.
Click to expand...

Not at all like that. It's not the OS that determines if data was read
correctly, it is the disk itself. On error the disk will report an error to
the OS.
 
Joep said:
It's a tad more complicated than that.


Not at all like that. It's not the OS that determines if data was read
correctly, it is the disk itself. On error the disk will report an error to
the OS.
Click to expand...

You're right, of course.
 
Hi,
Thanks for the info.

so after detecting bad sector, the disk report an error to the OS.
Where that Bad sector info will be stored : whether by the OS or in
disk itself. ?

-
Guru
 
Back
Top