This is a fast storage area that is not backed up – it is intended to be used as a temporary scratch space. Though it is not backed up, there is some built-in redundancy allowing the file servers to continue to function without loss of data if some hardware fails. If too much hardware fails simultaneously though, the file servers will lose data.

Generally, each Principal Investigator (PI) is given space in this storage area and that PI then splits it among their researchers. Usually this storage area can be accessed via the symbolic links ~/scratch/ and ~/common/ unless you deleted those symbolic links. The ~/scratch/ area is intended to be a scratch (temporary storage) space for your own files. The ~/common/ directory is for temporary files that you want to share between members of your research group.

The ~/scratch/ and ~/common/ are merely symbolic links to the 14 TB storage area – they are not actual directories. A symbolic link is like a pointer in C or a shortcut in Windows. It merely points to another file or directory or file. When you access a link in cd or another application, the application actually accesses the directory or file that the link points to. The ~/scratch/ symbolic link points to your scratch directory, and the ~/common/ symbolic link points towards your research group's shared storage area. Since those are symbolic links to directories, you can treat them as directories.

Data stored in ~/scratch/ and ~/common/ does not count towards your home directory quota. However, the filesystem on which your ~/scratch/ and ~/common/ data is stored has limited space. That space is shared by everyone who can write data to the filesystem (usually everyone in your research group). To determine how much space is free, run this command:

df -h ~/common/ ~/scratch/

For me, this prints out:

Filesystem            Size  Used Avail Use% Mounted on
thumper1-ib:/scratch/sparling
                      500G   44G  456G   1% /thumper1/scratch/sparling
thumper1-ib:/scratch/sparling
                      500G   44G  456G   1% /thumper1/scratch/sparling

You will get a similar message, but with different directory names and sizes. The 500GB 44GB 456GB lines tell you the storage limit, how much storage has been used, and how much space is still available. The first line that lists sizes is for ~/common/ (since you listed ~/common/ first in the df command) and the second line is for ~/scratch/. Note that there are no file limits – you can make as many files as you want so long as you don't use up all of the storage space. The filesystem itself has limits as to how many files and directories you can create, but those limits are usually very large.

The thumper1-ib:/scratch/sparling tells you where the data is physically stored. The thumper1-ib is the name of the remote machine that stores the data, and the /scratch/sparling tells you where on that machine the data is stored. The /thumper1/scratch/sparling tells you where that directory is mounted on the local machine. In other words, /scratch/sparling on thumper1-ib is accessible from /thumper1/scratch/sparling on the machine on which you ran df. Note that, in my case, the ~/scratch/ and ~/common/ directories are stored on the same filesystem (they are both on thumper1-ib:/scratch/sparling). Thus, any files I put in my ~/scratch/ or ~/common/ will count towards the same storage limit. In your case, those directories might be on different filesystems. If so, data stored in one directory will not count towards the storage limit of the other.

If you do not know where your Inifiniband-connected storage area is, contact your PI or user support.