Re: What happens to pages that failed to be written to disk?

[Szakacsits Szabolcs <szaka@sienet.hu>]

On Thu, 28 Jul 2005, Andrew Morton wrote:
> Martin Jambor <jamborm@gmail.com> wrote:
> >
> > Do filesystems try to relocate the data from bad blocks of the
> > device?

Only Windows NTFS, not others AFAIK (most filesytems can mark them during
mkfs, that's all).

> Nope.  Disks will do that internally.  If a disk gets a write I/O error
> it's generally dead.

That's what I thought also for over a decade (that they are basically dead
soon) so originally I disabled NTFS resizing support for such disks (the
tool is quite widely used since it's the only free, open source NTFS
resizer).

However over the last three years users convinced me that it's quite ok
having a few bad sectors (not only in the remapping area). I investigated
several "dead" disks and the pattern was that they had maximum a dozen bad
sectors, the disk quality didn't degrade in time and users sweared they
never had any problem (crash, data loss, corruption, whatever).

So recently I added optional support for working with such "dead" disks
and this is a bit frustrating since if users don't run badblocks in 
such cases when creating the Linux filesystems then they will have a
hopefully not too spectacular encounter with these sectors sooner or
later.

Of course I don't say that all disks having bad sectors are totally ok and
never will die. Only that that it seems some subset of them seems to keep
working perfectly fine (the issue looks similar to the "having a few dead
pixel" problem on some LCD's and laptops).

	Szaka