What is the advisability of running BOTH mysql and postgres on the same server?

I've got a couple websites that use mysql for backends for CMS, and an email system that I'd like to set up using postgres.

Is there any problem (performance or otherwise) in having both running at the same time?

I know the answer to that partially depends upon the server box and workloads, but assuming a relatively new setup with plenty of speed (single processor) and a low workload, are there any other 'gotchas' to be aware of?

Thanks
Kosuke

I seriously doubt there are any real problems in running both at the same time other than the load issues you already mentioned. About the only issue I can think of is having both listen to the same port, but I believe they listen to different ones as installed.

I have previously run both before, I don't think there will be any problem.

I am running both now, without trouble.