Re: Are linux-fs's drive-fault-tolerant by concept?

[Stephan von Krawczynski <skraw@ithnet.com>]

On Sun, 20 Apr 2003 17:40:29 +0100 (BST)
John Bradford <john@grabjohn.com> wrote:

> > > Fault tolerance in a filesystem layer means in practical terms
> > > that you are guessing what a filesystem should look like, for the
> > > disk doesn't answer that question anymore. IMHO you don't want
> > > that to be done automagically, for it might go right sometimes,
> > > but also might trash everything on RW filesystems.
> > 
> > Let me clarify again: I don't want fancy stuff inside the filesystem that
> > magically knows something about right-or-wrong. The only _very small_
> > enhancement I would like to see is: driver tells fs there is an error while
> > writing a certain block => fs tries writing the same data onto another
> > block. That's it, no magic, no RAID stuff. Very simple.
> 
> That doesn't belong in the filesystem.
> 
> Imagine you have ten blocks free, and you allocate data to all of them
> in the filesystem.  The write goes to cache, and succeeds.
> 
> 30 seconds later, the write cache is flushed, and an error is reported
> back from the device.

And where's the problem?
Your case:
Immediate failure. Disk error.

My case:
Immediate failure. Disk error (no space left for replacement)

There's no difference.


Thing is: If there are 11 blocks free and not ten, then you fail and I succeed
(if there's one bad block). You loose data, I don't.


Regards,
Stephan