Hi Walter.
I am assuming AEP means project file? If so, no, the project file is also on the server, not system drive.
If you meant AE program itself, then yes, on the system drive.
I am not sure how I would go about what you mentioned: “… move system’s global tmp directory to a different volume by pointing the /tmp symlink elsewhere ”
One other option i am experimenting with is disk cache.
I have it turned ON, and pointing to a RAID large enough to handle this, but will try with it OFF as well.