Re: Async I/O

Raw devices are required on DEC UNIX for Parallel Server because the devices cannot be shared by more than 1 node if they are 'normal' filesystems (until the next major release of the OS - 5 I think)

Regards

Alex

Stephane Faroult wrote:

> Hans-Peter Sloot wrote:
> >
> > Hello Stephane,
> >
> > I don't think that your statement is true.
> > Oracle will be clever enough to open the redo log files
> > with the O_SYNC flag.
>
> I would say it depends on operating systems. I distinctly remember
> (well, a long time ago : t'was v5 then) that on some ports the
> documentation was explicitly stating that the only way to guarantee
> integrity was to use raw devices. I have not studied it in detail, but I
> am ready to bet that it is a similar reason why raw devices are required
> on DEC/Unix for intance with the Parallel Server Option. And even if
> redo log files are synchronously written (right, the example was perhaps
> not the most appropriate), and control files too, there is some need of
> synchronization between data, redo and data files, since the data file
> header contains the system commit number which enables Oracle to require
> a recovery if needed on startup. Be certain that if the Oracle support
> discourages something, it means there is a potential risk, however small
> and unlikely.
>
> --
> Regards,
>
> Stéphane Faroult
> Oriole Corporation
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Received on Wed Mar 24 1999 - 03:02:57 CST