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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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