File Organization

All systems in the cluster share a common file structure via NFS, but not all disks are mounted on all other systems. Your disk allocation will depend on whether you are a MUN user or an external HPCnet user of Tempus.

MUN users

All MUN users have a home directory on a disk on Plato. This disk is shared with many other users and your quota here is quite small so it is typically not suitable for HPC use. In order to use the cluster, you need to have disk space allocated on one or more other disks. These disks are either mounted on Tempus or on the Alpha cluster. The disk you use will depend on which system you use to run your job.

External users

The situation is simpler for external users. You will be assigned disk space on disk /k1 which is available from both Tempus and Kronos. Your default home directory is the same on either system.

Use the quota command to see a list of all disks on which you have been allocated disk space and how much disk space you may use.

Available Disks
Filesystem NFS Host Size (GB) Also Mounted On
/h1
/hpc3
/h2
/k1 		Alcor
Alcor
Tempus
Tempus 		2
2
5
2 		Plato, Alioth, Alphaid, Mizar
Plato, Alioth, Alphaid, Mizar
Plato, Kronos
Kronos

In summary, Tempus users can use either /h2 or /k1 while users of the Alpha cluster can use either /h1 or /hpc3.

If you decide to use the Alpha cluster and your job is I/O intensive, you will probably want to ensure that the job is accessing local disk on the same system on which the job is running. This will help to minimize the network traffic involved in disk access which can be a limiting factor in job performance. For example, if your I/O intensive job is running on alioth and writing to the shared disk /h1 hosted on alcor, you will notice that the job will run much slower. For this reason, it is advised that you copy your files to /scratch, a separate local filesystem on each computer, before running your job. An example of this is found in the LSF FAQ.

Last modified February 14, 1997 by Allan Goulding