Checkpoints vs restartpoints

Hi

Why do standby servers not simply treat every checkpoint as a
restartpoint?  As I understand it, setting checkpoint_timeout and
checkpoint_segments higher on a standby server effectively instruct
standby servers to skip some checkpoints.  Even with the same settings
on both servers, the server could still choose to skip a checkpoint
near the checkpoint_timeout limit due to the vagaries of time keeping
(though I suppose it's very unlikely).  But what could the advantage
of skipping checkpoints be?  Do people deliberately set hot standby
machines up like this to trade a longer crash recover time for lower
write IO?

I was wondering about this in the context of the recent multixact
work, since such configurations could leave you with different SLRU
files on disk which in some versions might change the behaviour in
interesting ways.

-- 
Thomas Munro
http://www.enterprisedb.com