Speeding Up Virtualized Transaction Logging with vTrans

In a virtualized environment, when multiple co-located relational database engines update their data files on a shared storage device simultaneously, the transaction log files, which be scattered within different guest image files, introduce the random logging I/O easily. To cope with this issue, we propose vTrans, a novel I/O driver of virtualized transaction log file. Generally, vTrans uses the split I/O driver design. In each guest operating system a front-end driver is added to identify the transaction logging semantic from specific database engine. At the hypervisor layer a dedicated back-end driver consolidates all transaction logging I/Os from guest font-end drivers and then persist them into a consecutive data area on the shared storage device, resulting in the relatively sequential logging I/O. We implement vTrans in a QEMU system which deployed MySQL InnoDB database engine. The experimental result shows that vTrans can effectively improve the performance of random logging I/O in a virtualized system.