Research Of Virtual Disk Write Cache In Virtualization Environment

In virtualization environment, for the reason of high reliability some virtual machinesneed to adopt write-through policy for disk write-cache to ensure the data consistency. Butfor other virtual machines with I/O performance demand, adopting a disk write-back cacheis essential to guarantee the basic I/O performance. So, different requirement types ofvirtual machines have a debate on the use of disk write-cache. However, it has nocorresponding solutions for this issue in the current virtualization environment.A prototype system called VDWB solves the coexistence problem of reliable virtualmachines and I/O-bound virtual machines on the use of disk write-cache on the samevirtualization platform. The method is to use the write-through strategy for the bottomdisk write-cache to guarantee the data consistence and create a replaced write-cache calledVDiskCache at the Virtual Machine Manager layer for each VM with high I/Operformance demand to buffer the written data for making up the performance degradation.The controllablility of VDiskCache makes the virtual machine can real-time open or closethe corresponding VDiskCache according to the upper application demand change to meetthe reliability or I/O performance. Besides, the designed VDiskCache bandwidth controlalgorithm reduces the performance influence to reliable virtual machines by frequentrefresh of VDiskCache.The experimental results show that VDWB can solve the coexistence problem ofreliable virtual machines and I/O-bound virtual machines on the use of disk write-cache onthe same virtualization platform. In ahead of ensuring the data consistency of reliablevirtual machines, VDWB can guarantees the I/O performance for virtual machines withhigh performance demand that the system throughput improves100%compared tooriginal virtualization environment.