We're considering installing MySQL on the same database server that has been running SQL Server. From my research there are no technical issues running both concurrently, but I am worried that the performance will be affected. Is by default SQL Server set up to use all available memory for example? What should I look out for? Thanks
A default SQL Server installation allows consumption of all memory on the machine but it is easy configurable and the same thing goes for MySQL, so given that youre machine actually have the CPU power and IO system to run both and enough memory so that you have a large enough cache on both SQL Server and mySQL go ahead :-)
That would entirely depend on what the requirements of each of your databases were for size and memory, performance requirements, and uptime requirements. If this is just a development environment, you're probably in a safe position to pilot such a configuration. If you're considering a production environment, you might have to know exactly how the databases behave under load, and if they share disk volumes, will they create intolerable disk contention. Upgrades to MS SQL might require reboots, and thus, your MySQL instance uptime is subject to that as well. Pilot your changes in a development environment and see if it is performant.