MySQL on Ubuntu 32bits vs 64bits My web app server is running on Ubuntu 12.04 server 32bits.
The mysql db is going to be installed on a different Ubuntu 12.04 server. Should I use 32 bits for the server on which mysql is or 64 bits?

If the db server is 64bits, can it cause issues knowing that the webapp is running on a 32 bits or it does not matter at all?

Many thanks,
Roman
In 2014, using 32bit architecture for any critical app is insane. So, I would suggest: 


Upgrade your web-app server to 64bit (soon you will not find 32bit
editions for most software). It is not that hard and you get better memory management, performance with the exact same hardware. 
Still, if you do not want to do that, install MySQL DB (64bit edition) on a 64bit Ubuntu server to get at least there the benefits of a 64bit architecture. There is no danger when you interact with SQL queries if the architectures of the web-app server and the DB server are different. When (when and not if because it will happen eventually) you will be forced to change your web app server architecture, you will have one less thing to worry about.