Some interesting stuff about software boundaries and limits in SharePoint Server 2010 – take a look at the table below. You should make a distinction between hard limits (which you simply should not exceed) and soft limits – which are a sort of recommendation.
|Content DB Size||100 GB||200 GB|
|File Size||2 GB||2 GB|
|DB’s per web app||100||300|
|Site collection size||100 GB||100 GB|
|List items per view||2000||5000|
|Application Pools||8 per web server||10 per web server|
|Managed Paths||20 per web app||20 per web app|
|Documents in a library||30 million with nesting. Depends heavily on usage and size of the documents|
|Indexed items in search||50 million||100 million|
There is also a Technet article – SharePoint Server 2010 Capacity Management: Software Boundaries and limits – which provides some additional guidance – this also puts the numbers listed above a little more in perspective.
Content database sizes up to 1 terabyte are supported only for large, single-site repositories and archives with non-collaborative I/O and usage patterns, such as Records Centers. Larger database sizes are supported for these scenarios because their I/O patterns and typical data structure formats have been designed for, and tested at, larger scales.
For a full overview of the different white papers - check out SharePoint Server 2010 performance and capacity test results and recommendations.
In general the new scale targets for 2010 go above and beyond the ones set in 2007 but design is still important although it becomes more difficult to bring a farm down by just putting millions of docs in one library – check out It looks like you’re building a large library. Would you like help? as well as Working with large lists in SharePoint 2010 – List Throttling .