Big networks (banks, insurance companies) basically use one of two options most of the time. Oracle or SQL Server.
It only seems like it isn't when you read sites like Hacker News, where most of the posters are not working in big environments. Facebook is a large scale solution that doesn't use either, but their data management and caching is so bad nobody should be considering them as a best practice.
Google, Craigslist, Twitter, Wikipedia, Youtube and Netflix are just a few example which don't use Oracle or MS SQL Server either.
It's not about being big, banks and insurance companies simply have different requirements on how to access and store their data compared to most websites/services.
Granted (except Google) - but Twitter, Wikipedia and Craigslist are only big in comparison in terms of traffic. Most banks push more data through their network than most developers can conceive.
If you took all of the votes from the 2000 election in the United States (I'll save you the search - it was just over 100 million), it wouldn't even equal one day's ATM transactions in the U.S., and those transactions are a nonevent.
We all know that there is a lot of data being pushed in banks networks, but your ATM example may not be a very good one. The transactions you are talking about do not occur in a single bank.
Twitter in not only big in terms of traffic. 200 million tweets per day is not small, even if a tweet involves less processing than an ATM transaction.
You can also consider Facebook as an example of website dealing with big data.
This is correct; it's the companies that are heavily regulated that have a hard time choosing a nosql solution. The flexibility of SQL means you can create a report at any time. This is necessary when the government comes knocking wanting some specific data pronto.
It's not just regulation. It's a need to report at a granular level and slice data as many ways as possible. That's why Essbase is so popular, even though it's so poorly written.
Oracle, Sybase, DB2, SQL Server and Informix. The last company I worked for had all of them.
- Oracle and SQL Server: chosen by us
- Sybase and Informix: chosen implicitly by choosing applications that preferred them[1]
- DB2: Chosen by a company that we acquired
Oh and some MySQL and SQLite too.
[1] Yes they ran on Oracle too - but when 98% of a vendor's customers are on Informix or whatever, sometimes it's just less painful to go with the flow, so you have access to that community.
It only seems like it isn't when you read sites like Hacker News, where most of the posters are not working in big environments. Facebook is a large scale solution that doesn't use either, but their data management and caching is so bad nobody should be considering them as a best practice.