VMAR: Virtual Machine I/O Access Redirection to Optimize Instantiation Performance and Resource Utilization

A key enabler for standardized cloud services is the encapsulation of software and data into VM images. With the rapid evolution of the cloud ecosystem, the number of VM images is growing at high speed. These images, each containing gigabytes or tens of gigabytes of data, create heavy disk and network I/O workloads in cloud data centers. Because these images contain identical or similar OS, middleware, and applications, there are plenty of data blocks with duplicate content among the VM images. However, current deduplication techniques cannot efficiently capitalize on this content similarity due to their high overhead and complexity.

We propose a new simple and non-destructive deduplication layer tailored for the cloud: Virtual Machine I/O Access Redirection (VMAR). VMAR generates a block translation map when images are captured, and uses it to redirect accesses for identical blocks to the same filesystem address. This greatly enhances the cache hit ratio of VM I/O requests and leads to more than 50% performance gains in instantiating VM operating systems, and over 70% gain in loading application stacks. It also reduces the I/O resource consumption significantly. Another strength of VMAR is that it does not change the storage layout of VM images, and thus each VM can make an independent decision on whether to use VMAR. This allows cloud administrators to adopt VMAR in an incremental way.

By: Zhiming Shen, Zhe Zhang, Alexei Karve, Andrzej Kochut, Han Chen, Minkyong Kim, Hui Lei, Nicholas Fuller

Published in: RC25349 in 2012


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