[ubuntu-uk] mbr

[Liam Proven]

On 28 January 2012 20:14, Barry Drake <ubuntu-advertising at gmx.com> wrote:
> On 28/01/12 20:00, thegeeksquadron at ymail.com wrote:
>>
>> Just curious to know this, as I don't format disks too often, but does
>> formatting a HD rid it of any bad sectors? I assume not, but I'm a tad
>> perplexed!
>
> AFAIK the bad sectors on SMART aware drives are re-located and won't be
> restored when formatting.  Ubuntu is SMART-aware and tells you when a drive
> is in danger of failing.  Windows lets it fail catastrophically unless you
> have installed a SMART monitor application.  A few relocated sectors is OK.
>  However, even these are an indication that the drive is on its way to the
> great drive home in the sky, so best replace it while you can still get an
> error free copy.

SMART is something slightly different.

The transparent bad-sector remapping you describe happen on /all/
modern hard disks - strictly, on all that use Logical Block
Addressing, I believe. When the drive controller meets a block that
needed several retries to read its contents, it maps out the affected
block and substitutes one from a hidden reserve area.

This is invisible to the computer or the OS, which is why I call it
"transparent". The drive does it all on its own; no error is reported
up to the OS.

When the drive starts reporting bad blocks to the OS, that means that
the reserve area has been used up. This means that 10% or something of
the drive has gone bad; that in turn usually means that the drive is
failing and will die completely soon.

SMART is a reporting system. It tells the BIOS or the OS that the
drive is suffering from various kinds of error that suggest that it is
likely to fail soon. It's handy but it's imperfect: I have a couple of
drives that report SMART errors but actually work fine, and I have
seen approaching a hundred or so drives that have failed with no SMART
errors at all.

But given that disks are now cheap, better safe than sorry. It's
preferable to have it and to turn it on in the BIOS - and if your
machines are seldom rebooted, then to have SMART status monitoring in
your OS, too.


-- 
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