Re: SCSI vs. IDE performance test

Greg Stark wrote:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
>
> > I'm not at all sure what IDE drives do when they have a failure writing out
> > cached buffers; anyone have experience with that?
>
> There's a looooong discussion about this too on linux-kernel, search for
> "blockbusting". I think the conclusion is "it depends".
>
> Often write failures aren't detected until the block is subsequently read. In
> that case of course there's no hope. What's worse is the drive might not remap
> the block on a read, so the problem can stick around even after the error.
>
> If the write failure is caused by a bad block and the drive detects this at
> the time it's written then the drive can actually remap that block to one of
> its spare blocks. This is invisible to the host.
>
> If it runs out of spare blocks, then you're in trouble. And there's no warning
> that you're running low on spare blocks in any particular region unless you
> use special utilities to query the drive. Also if the failure is caused by
> environmental factors like vibrations or heat then you can be in trouble too.

My Buslogic/Mylex plain SCSI controller would beep when it hit a bad block ---
I didn't know why my computer was beeping for a while until I figured it out ---
can't beat that service.

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