For large user database websites, like myspace or facebook, what database do they use to store all the user info? Is it all MySQL?
doubt it, probably some big enterprise database software, where they pay 10s of thousands. hehe, i really dont know... varies depending on budget
Checkout Markus Frind's blog at http://plentyoffish.wordpress.com He's the one man band who started the dating site Plenty Of Fish and rakes in the big adSense dollars. If you dig into this blog, he shares how he got started and what he currently uses.
The larger companys I worked with all used Oracle and it's costing a little more then 10s of thousands more like 10s of millions in license fees
Google started AdWords on MySQL. Then moved to Oracle and got into deep shit. Can't remember the ending of it but I think they regretted it badly and now are on some custom deal. A quick Google found me this: http://xooglers.blogspot.com/2005/12/lets-get-real-database.html Can't find the original story in a hurry. DP runs on MySQL and all the tools + forum combined makes it a pretty big system.
I'll look into it. What are the reasons for not using MySQL? Does it start to slow down because the databases get so large? Does it have some limitations?
MySQL server is a good large database but it doesn't have the enterprise features of it's commercial counterparts. However it is improving over time and adding features. Features such as failover tollerance, views, indexed views, stored procs, integrity, etc. are missing / in development / new (probably need to check with mySQl to see what the latest verions is I havent paid a visit in a while.) It really depends on what you are trying to do and the size of tha database. I'd be woried about trusting Gigs of mission critical data to mySQL but website content forums etc would be fine.
When MySQL needs to scale, there's the option of using database replication with master and slave servers. This spreads the mysql load across a whole group of database machines. Most larger sites also have very good caching strategies. For an example of this, check out wikipedia's setup. http://meta.wikimedia.org/wiki/Wikimedia_servers
DrMalloc makes a good point, since I went .net with built in caching API I've been able to squeaze a hell of a lot more out of MS access nevermind enterprise class databases. This is very true if your database is mostly concerned with presenting and displaying data to the user. I've seen quite a few sites rewritten in .net to take advantage of this as it can save you serious £££ of investment on your database server(s).