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SubjectRe: RFC: from FIBMAP to FIONDEV
On Mon, Jun 14, 1999 at 06:50:20PM +0200, Werner Almesberger wrote:
> Matthew Wilcox wrote:
> > On Fri, Jun 11, 1999 at 12:42:15PM +0200, Werner Almesberger wrote:
> >> I'm not so sure what to do about RAIDs.
>
> Well, the longer I think about it, the less I'm convinced anything special
> should be done for RAIDs, except for issuing a warning and trying to get
> things to work in a non-redundant way.

Okay, I accept that there's probably no sensible way for LILO to deal
with RAID-[2345] right now. However, that doesn't mean we should design an
interface that can't support it in a sensible way. To me that means we
should have an index count passed to FIONDEV.

RAID 2,3,4,5 return the data block on the first call and set the
COPIES flag. Subsequent calls set the XOR flag to indicate that the
other blocks should be XORed together to recover the original block.
lilo is perfectly free to ignore this information, but maybe someday
we'll have a good way to use this information.

With RAID 1, lilo can install multiple copies of LILO, one on each disc,
each one told about the blocks which exist on its own disc.

--
Matthew Wilcox <willy@bofh.ai>
"Windows and MacOS are products, contrived by engineers in the service of
specific companies. Unix, by contrast, is not so much a product as it is a
painstakingly compiled oral history of the hacker subculture." - N Stephenson

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