Fault Tolerance with Virtual Disk Replicas in the Mass Storage Network

Data availability and accessing performance in large scale storage network have been more and more important. Based on the in-band virtualization system for massive storage, virtual disk replicas are proposed to improve the data availability. The replicas use selective read scheduling, asynchronous update mechanism, and a special space-adjusting algorithm to optimize the data accessing performance. The experiments with virtual disk replicas show that, when the device number is adequate, the read-performance can be increased by 26%; even if one or two disks fail, the I/O operations can be processed correctly, and the read-performance is still over 10% better than the normal accessing without replicas.