[Geocoding] Nominatim performance

[Cambridge Cycling Campaign - Simon Nuttall]

A whole world nominatim installation started on 2 Feb finished on 7
Mar, and is now running at:

http://nominatim.cyclestreets.net/

It has entered the catch up phase - which began with data from 21 Jan.

It seems to be taking a day to catch up with a day's updates - so it
is not making much progress and is heavily i/o bound, even on a 32GB
VM with 2 allocated processors.

Do all these timings seem normal?

What could I do to improve performance?

Simon