Using the local temporary filesystems

Introduction

Temporary filespace is traditional provided by a directory called /tmp. In many cases it is possible to use any of the SAN filesystems but sometimes it is better to use a local disk such as /tmp. There are large /tmp directories on all machines.

Location

The directory is located at /tmp and a second directory which exists for the duration of the job is located in /tmp which is called $TMPDIR.

Policies

• There is no back up policy on /tmp.
• There is a purge policy, files may last longer than a week though you should not expect them to last any longer than a week. Files in $TMPDIR will be cleared out when the job terminates.
• There is a quota on /tmp and it is fixed for all users.

Usage

On some occasions /tmp can provide greater performance than the SAN equivalent. These situations usually involve writing large files with small write statements, which in general is not good practice as it can lead to poor performance of the I/O.

Because /tmp is not directly accessible from most machines it is necessary to copy information to it in the batch job and from it at the end of the batch job if required.

Files can be purged from here so it is useful to keep copies of important files in either the home directories or stored offline on tape.