File Systems
Listed below are descriptions of the more important file systems on hydra.
Head Node
- /export
The /export file system contains application software and user home directories. It is hardware RAID 1
(mirror) for redundancy, and it is about 384GB in size. Quotas are enabled to limit users to a fixed amount
of space. Because it is NFS mounted to the compute nodes and reads/writes go over the network,
it should not be used for computational scratch space.
Regular Compute Nodes
- /scratch
/scratch is a 2-disk software RAID 0 (striping), about 434GB in size. It is faster than a single disk,
and it is local storage on each node. This is where compute jobs should put scratch files. The
queue system will automatically create a temporary directory in /scratch for each job and set the $TMP
environment variable to the name of the directory. When the job completes, the queue system will
automatically remove the temporary directory.
Whenever possible, the existing job submit scripts on hydra (gmssub, g03sub, etc.) will take the necessary steps to
use the temporary directories in /scratch. If you write your own submit scripts, you should do this
yourself.
Big Compute Node
- /scratch
On the "big" compute node, /scratch is a 4-disk hardware RAID 0 of about 893GB. Otherwise, it functions
just like /scratch on the regular nodes.
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