This paper presents the design, implementation, and evaluation of IO-Lite, a unified I/O buffering and caching system. IO-Lite unifies all buffering and caching in the system, to the extent permitted by the hardware. In particular, it allows applications, interprocess communication, the filesystem, the file cache, and the network subsystem to share a single physical copy of the data safely and concurrently. Protection and security are maintained through a combination of access control and read-only sharing. The various subsystems use (mutable) buffer aggregates to access the data according to their needs. IO-Lite eliminates all copying and multiple buffering of I/O data, and enables various cross-subsystem optimizations. Performance measurements show significant performance improvements on Web servers and other I/O intensive applications. 1 Introduction This paper presents the design, the implementation, and the performance of IO-Lite, a unified I/O buffering and caching system. IO-Li...

Realistic computer systems are hard to model using state-based methods because of the large state spaces they require and the likely stiffness of the resulting models (because activities occur at many time scales). One way to address this problem is to decompose a model into submodels, which are solved separately but which exchange results. We call modeling formalisms that support the exchange of results between models "connection formalisms." This thesis develops connection as a decomposition technique. The existing connection infrastructure in the Mobius modeling framework is used to develop a terminology to describe the decomposition of large models and the inherent associated problems. A theory is then developed to describe when such decompositions are feasible.

File system virtual appliances (FSVAs) address the portability headaches that plague file system (FS) developers. By packaging their FS implementation in a VM, separate from the VM that runs user applications, they can avoid the need to port the file system to each OS and OS version. A small FS-agnostic proxy, maintained by the core OS developers, connects the FSVA to whatever OS the user chooses. This paper describes an FSVA design that maintains FS semantics for unmodified FS implementations and provides desired OS and virtualization features, such as a unified buffer cache and VM migration. Evaluation of prototype FSVA implementations in Linux and NetBSD, using Xen as the VMM, demonstrates that the FSVA architecture is efficient, FS-agnostic, and able to insulate file system implementations from OS differences that would otherwise require explicit porting.

File system virtual appliances (FSVAs) address the portability headaches that plague file system (FS) developers. By packaging their FS implementation in a VM, separate from the VM that runs user applications, they can avoid the need to port the file system to each OS and OS version. A small FS-agnostic proxy, maintained by the core OS developers, connects the FSVA to whatever OS the user chooses. This paper describes an FSVA design that maintains FS semantics for unmodified FS implementations and provides desired OS and virtualization features, such as a unified buffer cache and VM migration. Evaluation of prototype FSVA implementations in Linux and NetBSD, using Xen as the VMM, demonstrates that the FSVA architecture is efficient, FS-agnostic, and able to insulate file system implementations from OS differences that would otherwise require explicit porting.