Kb31

Emulab FAQ: Using the Testbed: What is Swapping?

Swapping is when you (or we, or the Emulab system) temporarily swaps out your experiment, releasing all of the nodes in the experiment. Your experiment is still resident in the Emulab database, and you can see its status in the web interface, but no nodes are allocated. Once an experiment is swapped out, you can swap it back in via the web interface by going to the Experiment Information page for your experiment, and clicking on the swapin option. You can also modify it.

The idle-swap checkbox in the Begin Experiment web page is used to determine what experiments can be automatically swapped by the testbed scheduling system. Note that all experiments are capable of being swapped; even if you do not check the idle-swap box, you are free to swap your own experiments as you like. The only difference is that the testbed scheduling system will not consider your experiment when looking for experiments to swap out. You will sometimes notice that the Experiment Information page does not contain the swap link. That is because experiments cannot be swapped when they are in transition. For example, when the experiment is being swapped in (say, after first being created) the link will disappear until the experiment is fully swapped in, and it is capable of being swapped out. You will need to occasionally reload the page so that the updated state is recognized and the swap link appears.

Be aware that we do not currently save any files that you may have placed on your nodes. When your experiment is swapped back in, you will likely get different nodes, with fresh copies of the disk images. For that reason, you should not swap your experiment out unless you make arrangements to save and restore any state you need.

Please be sure to read our Node Usage Policies, which contain detailed information on swapping.