Rather than looking for generalized optimizations pedantically, you could look into making the system faster for one (or more, but a few) "common" usage scenario.
There can be numerous minor and mundane performance improvements, even if they are technically unimpressive/uninteresting, or ugly/kludgy to implement. Together, such improvements could lead to a perceptible performance gain from the users' point of view.
Varying the granularity at which you would usually make improvements. For example, in addition to improving typical OS algorithms, you could look into improving more meta operations, such as the entire boot process.
The most important kind of performance is the one perceived by the eventual users of a system. Thus, in any usage scenario, a "faster workflow" would be tantamount to "higher performance". It might be possible to make the workflow faster without making fundamental changes in the design and implementation of the components involved. With a prior knowledge of how the system would be typically used, you could rearrange the order in which things happen (even if the resulting order is unnatural or unclean), if doing so makes the user believe that things are happening faster.
The cornerstone, perhaps the foundation, of establishing a grid is a well-defined security policy and implementation. Any organization with expensive equipment and sensitive data, whether it is government sensitive, or company private data, has security policies in place to protect that data, both physically, and electronically. Several areas should be described in the Security Policy. One such area is authentication of individuals and entities.