Re: Raw devices (was Re: Berkeley DB license)

Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>> The only (completely) real solution for this is to use raw devices,
>> uncached by the kernel, without any filesystem overhead...
>> Are there any plans to support that?

> No specific plans. afaik no "anti-plans" either, but the reason that
> we don't do this yet is that it isn't clear to all of us that this
> would be a real performance win.

... whereas it *is* clear that it would be a portability loss ...

> If someone wanted to do it as a project that would result in a
> benchmark, that would help move things along...

I think we'd want to see some indisputable evidence that there'd be
a substantial gain in the Postgres context. We could be talked into
living with the portability issues if the prize is worthy enough;
but that is unproven as far as I've seen.

At the moment, we have a long list of known performance gains that we
can get without any portability compromise (for example, the lack of
pg_index caching that we were getting our noses rubbed in just this
morning). So I think none of the key developers feel particularly
excited about raw I/O. There's lots of lower-hanging fruit.

Still, if you want to pursue it, be our guest. The great thing
about open-source software is there's room for everyone to play.

regards, tom lane