Every user of the system produces data, that has to be stored somewhere. Usually files go into the home directory, but this is not the only option. Experienced users are offered more storage options for larger amounts of data, each of which has certain characteristics. The following is an overview of the different alternatives.
Your saved files usually go here. Every user has his own home directory, which only he has access to. The data is stored on a fileserver in the computer lab and is mounted onto the computer you log into via the network. Hence, the transfer of data is not as fast as it is with a local harddrive. Since all homes are stored on a single machine with limited capacity, the space available to an individual user is limited as well. That is why larger files (that is, files larger than a gigabyte) should be saved to a different storage location.
In /vol/tmp/USERNAME, every user has access to another location for storing files. (Here, USERNAME has to be replaced with your actual login name). This directory has about the same properties as the home directory. It is stored on a server in the computer lab and is backed up every night. Just like with the home directory, the users have to share a limited amount of space. To find out how much free space there is left (for all users together), use the following command:
df -h /vol/tmpThe output looks something like this:
| Filesystem | Size | Used | Avail | Use% | Mounted on |
| volumes:/volumes/tmp | 450G | 313G | 138G | 70% | /vol/tmp |
The column labelled Avail shows the space that is left, in this case it is 7.7 GB. If a file is larger than the available space, the local directories /var/tmp are a suitable alternative.
The directory /var/tmp is available to every user on every computer. It is located locally on the computer's harddrive and is not being backed up. Therefore, the data is not proteced against hardware failure, and may also disappear upon exchange of the computer or reinstallation. As a consequence, /var/tmp should be used only for temporary storage, e.g. output of simulations before postprocessing, or for data which can easily be reproduced or downloaded again. If you want to use /var/tmp, create a direcory with your username there, and make sure only you have permission to access the files in this directory. The capacity of /var/tmp can be inspected with the command df -h /var/tmp which gives an output like this:
| Filesystem | Size | Used | Avail | Use% | Mounted on |
| /dev/sda4 | 43G | 24G | 17G | 60% | /var/tmp |
In the following table we have summarized the characteristics of the different storage places to allow for an easy overview:
| Name | Location | Size | Fast Access |
Availability | RAID | Backup | Lifetime | Private Directory |
| /homes | Server | + | + | + | + | + | ∞ | + |
| /vol/tmp | Server | + | + | + | + | + | ∞ | + |
| /var/tmp | local | +/++ | +++ | - | - | - | +/- | +/- |