Running Jobs Across the Cluster

Directed Execution with bpsh

In the directed execution mode, the user explicitly defines which node (or nodes) will run a particular job. This mode is invoked using the bpsh command, the ClusterWare shell command analogous in functionality to both the rsh (remote shell) and ssh (secure shell) commands. Following are some examples of using bpsh:

• This example runs hostname on the compute node and writes the output back to the user's screen from compute node 0:

  [user@cluster user]$ bpsh 0 /bin/hostname .0

• The following example runs the uptime utility on node 0, assuming it is installed in /usr/bin:

  [user@cluster user]$ bpsh 0 /usr/bin/uptime 12:56:44 up 4:57, 5 users, load average: 0.06, 0.09, 0.03

Dynamic Execution with beorun and mpprun

In the dynamic execution mode, Scyld decides which node is the most capable of executing the job at that moment in time. Scyld includes two parallel execution tools that dynamically select nodes, beorun and mpprun. They differ only in that beorun runs the job on the selected nodes concurrently, while mpprun runs the job sequentially on one node at a time.

The following example shows the difference in the amount of time the system uses to run a command with beorun vs. mpprun:

[user@cluster user]$ date;beorun -np 8 sleep 1;date
  Fri Aug 18 11:48:30 PDT 2006 
  Fri Aug 18 11:48:31 PDT 2006 

[user@cluster user]$  date;mpprun -np 8 sleep 1;date
  Fri Aug 18 11:48:46 PDT 2006 
  Fri Aug 18 11:48:54 PDT 2006