The case for active block layer extensions
ACM SIGOPS Operating Systems Review
Support for automatic diagnosis and dynamic configuration of scalable storage systems
Euro-Par'06 Proceedings of the CoreGRID 2006, UNICORE Summit 2006, Petascale Computational Biology and Bioinformatics conference on Parallel processing
Extensible block-level storage virtualization in cluster-based systems
Journal of Parallel and Distributed Computing
DARC: design and evaluation of an I/O controller for data protection
Proceedings of the 3rd Annual Haifa Experimental Systems Conference
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In this work we propose Violin, a virtualization framework that allows easy extensions of block-level storage stacks. Violin allows (i) developers to provide new virtualization functions and (ii) storage administrators to combine these functions in storage hierarchies with rich semantics. Violin makes it easy to develop such new functions by providing support for (i) hierarchy awareness and arbitrary mapping of blocks between virtual devices, (ii) explicit control over both the request and completion path of I/O requests, and (iii) persistent metadata management. To demonstrate the effectiveness of our approach we evaluate Violin in three ways: (i) We loosely compare the complexity of providing new virtual modules in Violin with the traditional approach of writing monolithic drivers. In many cases, adding new modules is a matter of recompiling existing user-level code that provides the required functionality. (ii) We show how simple modules in Violin can be combined in more complex hierarchies. We demonstrate hierarchies with advanced virtualization semantics that are difficult to implement with monolithic drivers. (iii) We use various benchmarks to examine the overheads introduced by Violin in the common I/O path. We find that Violin modules perform within 10% of the corresponding monolithic Linux drivers.