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SubjectRe: lack of raw disk devices
On Sun, Jan 04, 1998 at 11:48:50AM -0500, linux kernel account wrote:

> On Sun, 4 Jan 1998, Harald Milz wrote:
>
> > Marty Leisner (leisner@sdsp.mc.xerox.com) wrote:
> > > I understand linux doesn't have raw devices because
> > > we don't need it.
> >
> > We actually do. A couple of database product make use of raw devices if
> > they exist, e.g. Oracle.
>
> They are just looking for excuses.. They could use whats already there..
> They just would have to deal with the fact that the OS is going to cache
> things in ways they dont like..

In a way that makes error recovery impossible for the database.

> They want to have complete input/output cach control.. Yes, that would be
> important if Linux was their prime target..

Customer calls Oracle (Sybase etc.): ``Your friggin database engine fucked
my entire 1TB database. I hope your competition does better ...''

Cite manual of xy-db ... ``Linux: We're sorry, if your box should crash, your
database might be fried'' ...

Wouldn't that be good promotion?

> But they could just say 'the
> Linux version is beta/not as good and stable because of it' and when they
> decide that Linux was a platform they really like: They could make a
> friggen kernel module to provide a raw interface.

That would be a horrible hack that'd break once a new kernelpatch is
released. And that's still the least problem.

This is not a vote for a blind implementation of raw devices. Raw devices
have their problems by design, mainly because of a lack of communication
between the buffercache and the userspace cache in the db engine.

Ralf

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