All programs in the QuickSilver distributed system behave atomically with respect to their updates to permanent data. Operating system support for transactions provides the framework required to support this, as well as a mechanism that unifies reclamation of resources af- ter failures or normal process termination. This paper evaluates the use of transactions for these purposes in a general purpose operating system and presents some of the lessons learned from our experience with a complete running system based on transactions. Examples of how transactions are used in QuickSilver and mea- surements of their use demonstrate that the transaction mechanism provides an efficient and powerful means for solving many of the problems introduced by operating system extensibility and distribution.

The Swift I/O architecture is designed to provide high data rates in support of multimedia type applications in general purpose distributed environments through the use of distributed striping. Striping techniques place sections of a single logical data space onto multiple physical devices. The original Swift prototype was designed to validate the architecture, but did not provide fault tolerance. We have implemented a new prototype of the Swift architecture that provides fault tolerance in the distributed environment in the same manner as RAID levels 4 and 5. RAID (Redundant Arrays of Inexpensive Disks) techniques have recently been widely used to increase both performance and fault tolerance of disk storage systems. The new Swift/RAID implementation manages all communication using a distributed transfer plan executor which isolates all communication code from the rest of Swift. The transfer plan executor is implemented as a distributed finite state machine which decodes and executes ...