What's The Best Linux Distribution For Clustering?

syn1 asks: "There has been a proliferation of Linux distros over the last couple years. Many are specialized for specific tasks or needs. In terms of Beowulf Clusters, there are a growing number of distros specialized for these clusters. Although the old favorite among specialized Beowulf distros is Extreme Linux, other distros such as Syclid Linux and Scali Linux are catching up in terms of user share. Additionally, more people are using conventional distros (Red Hat, Debian, Mandrake, SuSE, etc..) and adding Beowulf support. I am just wondering what fellow Slashdotters think about these various distros when it comes to Beowulf Clusters and which ones they think are best."