Vtrim: A Performance Optimization Mechanism for SSD in Virtualized Environment

Solid state disk, compared with hard drive disk, has low delay, low energy consumption, high throughput, high bandwidth, and many other advantages. But it is important that, we will meet challenges when using the solid state disk in virtualized environment, because of its own structure and characteristics. But the trim instruction, that plays an important role in space management of SSD, cannot be passed through in a virtualized environment to the underlying solid state disk. So, how to make the trim instruction be handled in virtualized environment will be an urgent problem. An optimized system used in virtualized environment, named Vtrim, is proposed to solve the problem. In the paper, Vtrim monitors the deletion operation in virtual machine and sends the deletion semantic to the Domain 0 immediately. Then the deletion semantic from virtual machine will be translated into the deletion operation in Domain 0. This deletion operation can punch hole on virtual machine disk image, then trigger the trim instruction. In this way, the performance of the SSD in virtualized environment will be improved greatly. Experiments prove that the random write performance will be improved more than 100% at most in the para-virtualization virtual machine with the Vtrim. The average response time will also be reduced to about 40% of the original one in the best case.