Guidelines-Dept of Physics - Carnegie Mellon University

Physics Department Computing Facility: Guidelines

The Physics Department maintains this cluster of computers for research-oriented and general purpose computing by physics graduate students, faculty, staff and visitors. We ask users to note these guidelines governing use of the cluster. The purpose of these suggestions is to enhance the utility of the cluster for all users and to ensure equitable sharing of the resources. Users must also follow the CMU computing policy.

Cleanliness and consideration

Food and drink are prohibited. When talking, please respect others working nearby. Log off when not actively using computer and clean up your work area when you are done. Feel free to clean off keyboards, monitors and mice when they need it. Place uncollected printer output in the racks closest to the printer. Make use of the paper recycling and waste baskets.

Disk space

A certain fraction of the disk space is available for users to store their own files and programs. This disk space is NOT backed up, so use at your own risk. USB drives and CD writers are available for you to perform your own backup on XP and Linux. A separate guide to using removable media on Linux is available. On unix/Linux systems ample local storage is available in /usr/user. In contrast, /tmp is kept nearly empty at all times for emergency storage space. Files in /tmp will be subject to removal without warning. For storage needs in the range of 10-75 MB your best solution is probably a "project volume" on the Andrew system. This space is backed up and automatically shared on all Andrew system computers. On XP systems user space is available on the D:\ drive. On Macintosh computers make yourself a folder in User. Users taking large amounts of disk space on any system may be asked to cut back to make room for others.

CPU time

Linux systems support remote login and running of background jobs. For this reason you should NEVER reboot a linux computer in the public cluster. To ensure that background jobs do not interfere with interactive computer use, and to ensure equitable sharing of CPU time, we ask background job users to follow these rules:

  • Nice the job at level 15. A typical syntax to follow is
    nice +15 program_name < input_file > output_file &
  • No more than one background job/person/CPU.
  • No more than two background jobs/computer (total, among all users) on a single processor computer or three jobs/computer on a dual processor computer.

To check the load on a computer use one of the commands w or ps aux or top. To check the load on another computer (without having to log in) use the command
rsh w.

Note that you are allowed up to two simultaneous jobs on a dual processor computer. This equals the processing power you can get using parallel processing (with MPI or open MP). Please do not use parallel processing unless you have proven through careful benchmarking that your program attains high parallel efficiency.


Printing is presently provided free of charge. Please do not abuse this privilege, or a printing charge may be imposed in the future. Use hpcolor for color printing only. Use duplex (two sided) printing on Osage to conserve paper. Be certain to use the correct transparency type in laser printers. Sign out transparencies on the sheet provided. Bring paper from stockroom when supplies run low in the cluster.


The people responsible for maintaining the computer cluster rely on individual users to report problems and offer ideas for improvements. Please contact the cluster manager: Al Brunk, 412-268-2736, Thank you for taking an active interest in maintaining this facility.