Re: Corruption Stats (fwd)

Rogier Wolff (
Thu, 30 Jul 1998 09:39:03 +0200 (MEST)

Linus Torvalds wrote:
> On Thu, 30 Jul 1998, Stefan Traby wrote:
> >
> > BTW: A drive following the SCSI-specs may cause disk-corruption
> > under Linux (WCE=1). Data may still be in write-cache after
> > shutdown and power-off. (I miss "synchronize cache").
> > This is for shure a theoretical problem, but a practical bug.
> > Or did I miss something ?
> No, you didn't miss anything.
> The thing has been discussed occasionally (very occasionally), and I don't
> know what the proper response is. According to some people the better
> drives make sure that they have enough rotational energy that they can
> make sure they get their data written out even after powerdown, but
> personally that sounds like science fiction to me (oh, I wouldn't be
> surprised if there are some drives that do it, but I'd be surprised if
> it's universal).

It is VERY hard to use the rotational energy to write more than just
one block. You would have the disk already spinning down, and you
might still have to do a few seeks, and you still have to write a
properly synchronized track.

This "feature" was specified on a DEC 1.6G SCSI disk that we bought
back in about '90. It said:
The disk has enough power to finish writing a sector should the
power go down.

Thus any sector it would start writing, it would finish, even if the
power goes down.

But that was just ONE sector.


Actor asks a collegue: "To what do you owe your success in acting?"
Answer: "Honesty. Once you've learned how to fake that, you've got it made."
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