Date: Tue, 11 Apr 2000 21:32:03 -0500
From: Ed Carp <erc@pobox.com>
> According to bert hubert:
> > If you have a bad block on a modern disk it is time for an instant
> > backup-and-replace. The concept of a 'bad bit' on a disk is pretty
> > much dead.
>
> What he said. I wouldn't bother putting a lot of intelligence into
> handling of bad blocks; trying to keep a failing disk alive is false
> economy of the worst kind.
It must be nice to live in such a perfect world where one can replace
disks instantly at the first sign of a problem. Why have such
badblock code in the kernel in the first place -- just insist that
all your users have error-free drives.
But out here in the real world we don't have such a luxury. It could
be days before a drive can get replaced. In the meantime, we have to
make do.
But wait a moment! I thought you said you had a high-reliability
requirement. If so, what the heck are you using a single unprotected
IDE disk?!? I've seen disks go from the first error to almost complete
failure in *hours*, and disks very much have finite, but variable,
lifetime, especially if they are put in heavy use or put into service in
harsh environments.
In the real world, if you really have that kind of requirement for
long-term, it-must-always-be-working reliability, you really should
either be using RAID, or some kind of silicon disk, depending on the
application.
If the customer isn't willing to pay that kind of money for that kind of
reliability, then he probably doesn't want that kind of reliability
badly enough. And if he really does, but refuses to invest the right
amount of resources to make it happen, and then is going to blame you
for not being able to violate the laws of physics, you probably don't
want that person as your customer....
- Ted
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