Storage and file management: Difference between revisions

When your account is created on a cluster, your home directory will not be entirely empty. It will contain references to your scratch and [[Project layout|project]] spaces through the mechanism of a [https://en.wikipedia.org/wiki/Symbolic_link symbolic link], a kind of shortcut that allows easy access to these other filesystems from your home directory. Note that these symbolic links may appear up to a few hours after you first connect to the cluster. While your home and scratch spaces are unique to you as an individual user, the project space is shared by a research group. This group may consist of those individuals with an account sponsored by a particular faculty member or members of a [https://www.computecanada.ca/research-portal/accessing-resources/resource-allocation-competitions/ RAC allocation]. A given individual may thus have access to several different project spaces, associated with one or more faculty members, with symbolic links to these different project spaces in the directory projects of your home. Every account has one or many projects. In the folder <code>projects</code> within their home directory, each user has a link to each of the projects they have access to. For users with a single active sponsored role, it is the default project of your sponsor while users with more than one active sponsored role will have a default project that corresponds to the default project of the faculty member with the most sponsored accounts.

* '''HOME:''' While your home directory may seem like the logical place to store all your files and do all your work, in general this isn't the case; your home normally has a relatively small quota and doesn't have especially good performance for writing and reading large amounts of data. The most logical use of your home directory is typically source code, small parameter files and job submission scripts.  

* '''PROJECT:''' The project space has a significantly larger quota and is well adapted to [[Sharing data | sharing data]] among members of a research group since it, unlike the home or scratch, is linked to a professor's account rather than an individual user. The data stored in the project space should be fairly static, that is to say the data are not likely to be changed many times in a month. Otherwise, frequently changing data, including just moving and renaming directories, in project can become a heavy burden on the tape-based backup system.  

* '''SCRATCH''': For intensive read/write operations on large files (> 100 MB per file), scratch is the best choice. However, remember that important files must be copied off scratch since they are not backed up there, and older files are subject to [[Scratch purging policy|purging]]. The scratch storage should therefore be used for temporary files: checkpoint files, output from jobs and other data that can easily be recreated.

* '''SLURM_TMPDIR''': While a job is running, <code>$SLURM_TMPDIR</code> is a unique path to a temporary folder on a local fast filesystem on each compute node reserved for the job. This is the best location to temporarily store large collections of small files (< 1 MB per file). Note that this space is shared between jobs on each node and the total available space depends on the node specifications. Finally, when the job ends, this folder is deleted. A more detailed discussion of using <code>$SLURM_TMPDIR</code> is available at [[Using_$SLURM_TMPDIR | this page]].

While the command '''diskusage_report''' gives the space and file count usage per user on ''home'' and ''scratch'', it shows the total quota of the group on project. It includes all the files from each member of the group. Since the files that belong to a user could however be anywhere in the project space, it is difficult to obtain correct figures per user and per given project in case a user has access to more than one project. However, users can obtain an estimate of their space and file count use on the entire project space by running the command