> Date: Sat, 3 May 1997 19:38:32 +1200 (NZST)
> From: "J. Sean Connell" <ankh@canuck.gen.nz>
>
> Even though it would require a total overhaul of every filesystem
> and the VFS layer, it doesn't seem to me that I could cheerfully
> use Linux in a zero-fault-tolerance environment when the fs code
> simply disowns the fs when it finds a single measly bad block...
>
> The entire VFS layer is going to be overhauled in the near future, and
> such issues will be considered heavily along the way.
>
> (As a side note, in a "zero fault tolerance" environment, you wouldn't
> buy disks which could ever report bad blocks, you'd use some sort of
> RAID strategy, all done in hardware, all mirrored and parity checked,
> where it's "bad block, what's that?")
Even then you currently run into trouble.
In case of a failure of an element in a RAID array, your "transaction
time" gets absolutely undeterminable. The current SCSI code is not
able to handle this and will basically freak out and start issuing
aborts and resets. All the logic when a command times out and how to
handle it (ie. all the strategy decisions) will have to be moved in the
lowlevel drivers since this is the only place where such decisions can be
made.
Mike