/scratch, which is a 1TB free-for-all filesystem. The general rule for using
/scratch is not to be a dick. Don't gobble up all the space. Users are encouraged to use it for good, and especially for datasets or intermediate code in large compiles that would otherwise exceed their normal quota.
There is no expectation of data permanence in
/scratch; data could be cleared out at any time by syscom. That being said, notice should be given unless there are special circumstances that warrant otherwise.
/scratch is exported over NFS, but it will be fastest if accessed from
corn-syrup, and it's recommended that any computations or compilations be done on that machine.