Re: Raw device I/O for large objects

Georgi Chulkov <godji(at)metapenguin(dot)org> writes:
> I am looking into implementing raw device I/O for large objects into
> PostgreSQL (maybe for all storage, I'm not sure which would be
> easier/better).

We've heard this idea proposed before, and it's been shot down as a poor
use of development effort every time. Check the archives for previous
threads, but the basic argument goes like this: when Oracle et al did
that twenty years ago, it was a good idea because (1) operating systems
tended to have sucky filesystems, (2) performance and reliability
properties of same were not very consistent across platforms, and (3)
being large commercial software vendors they could afford to throw lots
of warm bodies at anything that seemed like a bottleneck. None of those
arguments holds up well for us today however. If you think you want to
reimplement a filesystem you need to have some pretty concrete reasons
why you can outsmart all the smart folks who have worked on
your-favorite-OS's filesystems for lo these many years. There's also
the fact that on any reasonably modern disk hardware, "raw I/O" is
anything but.

My opinion is that there is lots of lower-hanging fruit elsewhere.
You can find some ideas on our TODO list, or troll the pghackers
list archives for other discussions.

regards, tom lane