Showing posts from May, 2011

Seeding Java Authorization and Authentication using /dev/urandom

We had a strange issue during Oracle WebLogic development yesterday. Setting up a secure connection between a client and the WebLogic Admin server took really long on our shiny new hardware (Dell R710) compared the older servers (Dell 2950). After we made sure everything was exactly the same, people started to blame C1 and C1E states and other powersave or cpu throttling measures. However, given the different in setup times (2-6 sec vs 50-90 sec), I suspected it to be something else. Throttling down from 2.23 GHz to 1.6 GHz cannot cause such a great difference. Or at least be unlikely.

Lo and behold, it turned out to be related to the seeding of the random number generator in Java. Normally this is linked to /dev/random but can be sped up by using /dev/urandom, which uses some entropy of your system. Still, the urandom device, while faster, still caused a 20-fold difference.

As a workaround, you can tell your JVM which seed generator to use and prevent JVM from waiting or looking or wha…

Dell Hardware repo mirror

The kind people of the German university of Göttingen have mirrored the Dell OMSA hardware and firmware repo for us.

This way, we have a European mirror available that is also much faster than Dell's native server.