3.B: What About X Stations?

3: Physics Department Cluster

3: Physics Department Cluster

Your best bet is to do your work on whichever machine has the fewest users or jobs to do. (The exception being hermes which is reserved for Web serving and should not be used for direct computations.) Yet you must log on to some machine before you can determine the workload on the cluster (we describe how to do that soon). An open console is a good machine to start with, or use an X station to a machine which does not get much use.

In the Department Cluster, the DEC's are somewhat faster machines than the IBM's and they may seem like the best choice. But remember that two users on a "fast" machine is probably slower than one user on a "slow" machine (the fast machines are hardly ever twice as fast at complete calculations). At present, the DEC's have the additional workload of maintaining the file system and are popular because they have been around longer, so they may be faster, but also slower for you to get your work done on.

However, if you need more than the 32 MB of RAM that are on the IBM's, then the DEC's with 64 MB would be preferred. (If you need more than 64 MB, you should look for a research computer because your job will need virtual memory and that is slow.)

Once you are logged onto a machine, you can determine the other users on that machine with the users command:

> users

You can find out about users on the machines goophy and banana by executing users as a remote shell (rsh) command:

> rsh goophy users
> rsh banana users

> rwho

Now this is a little fancy, but if you really want to see all the processes on a machine, use the processes (ps) command:

> ps -ef|grep -v root

Here we have used a | to "pipe" the output of ps through the grep command to remove ("veto") all processes being run by root.

Because machine speed is dependent on workload, which machine is fastest may depend on the time of day (the familiar afternoon brownout). Keep in mind that even though you are logged on to one machine, you can easily open a window to another and do your work on it. (Try clicking the different mouse buttons in