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Recent research on distributed shared memory DSM has focussed on improving performance by reducing the communication overhead of DSM. Features added include lazy release consistency-based coherence protocols and new interfaces that give programmers the ability to hand tune communication. These features have increased DSM performance at the expense of requiring increasingly complex DSM systems or increasingly cumbersome programming. They have also increased the computation overhead of DSM, which has partially o set the communicationrelated performance gains. We c hose to implement a simple DSM system, Quarks, with an eye t o wards hiding most computation overhead while using a very low latency transport layer to reduce the e ect of communication overhead. The resulting performance is comparable to that of far more complex DSM systems, such a s T readmarks and Cashmere.

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The lack of a flexible consistency management solution

Essentially all distributed systems, applications, and services at some level boil down to the problem of managing distributed shared state. Unfortunately, while the problem of managing distributed shared state is shared by many applications, there i s n o c ommon means of managing the data every application devises its own solution. We have developed Khazana, a distributed service e x p orting the abstraction of a distributed p ersistent globally shared store that applications can use to store their shared state. Khazana is responsible for performing many of the common operations needed b y distributed applications, including replication, consistency management, fault recovery, access control, and location management. Using Khazana as a form of middleware, distributed applications can be quickly developed f r om corresponding uniprocessor applications through the insertion of Khazana data access and synchronization operations.