Many builds freeze if built in parallel. They tend to freeze during SVN operations, especially checkout. The solution was to double the open file handles number.

I start 3 Hudson builds on the same physical Hudson node.
First, three build executors check out subversion source. And… they tend to freeze.
Not only they freeze for some time. They actually stop reacting and if it kills this build, next will never work.

Doubling the number of file handles solved is:

ulimit -n 2048