Re: Understanding Execution Plans

Oliver Weichhold <oliver(at)weichhold(dot)com> writes:
> It seems that especially the joins take extremely long on the VPS versus the
> dedicated machine but I'm not sure if that's caused by the the fact that the
> dedicated machine has 8x the amount of RAM and thus can cache much more data
> or because it has more I/O bandwidth due to the exclusive access to the
> harddisk or a combination of both. Any suggestions?

I'd guess that your virtual machine is delivering seriously bad disk
access performance. The relative lack of RAM certainly isn't helping
though; if it had more then the kernel disk buffers could mask the poor
I/O to some extent.

You could perhaps fix the blame more accurately by doing some disk
benchmarking with bonnie or a similar tool.

regards, tom lane