I've not been posting a lot about my studies on bottlenecks in the
server and my work on what I am seeing with different engines, but I
thought I would comment on Peter's benchmarks on PBXT:
This is a bit off what I have found so far:
In all tests but the final, the task was to split a load among many connections and see how the engine behaved. PBXT's write performance is quite good. Its update crashed on me before I got to see how well it would perform and the scan read was awful. On the other hand its performance with mixed IO is quite good. For an engine at this point in its integration, these are all promising numbers. I've got little doubt about PBXT being an engine that people will use in production.
All numbers were performed on 5.1, and I used PBXT as a loadable engine (aka it was not statically compiled in).
If you are curious about the script I used to generate these numbers you can grab it here: