FITDOC: fast virtual machines checkpointing with delta memory compression

Abstract

Virtualization provides the function of saving the entire status of the execution environment of a running virtual machine (VM), which makes checkpointing flexible and practical for HPC servers or data center servers. However, the systemlevel checkpointing needs to save a large number of data to the disk. Moreover, the overhead grows linearly with the increasing size of virtual machine memory, which leads to disk I/O consumption disaster along with poor system scalability. To target this, we propose a novel fast VM checkpointing approach, named Fast Incremental checkpoinTing with Delta memOry Compression (FITDOC). By studying the runtime memory characteristics of different workloads, FITDOC counts the dirty pages in a fine-granularity manner (i.e., the number of 8 bytes), instead of in the conventional method (i.e., the number of pages). FITDOC utilises a dirty page logging mechanism to record the dirty pages. Accordingly, a delta memory compression mechanism is implemented to eliminate redundant memory data in checkpointing files. To locate the dirty data in dirty pages, FITDOC utilizes two mechanisms: by analyzing the distribution characteristics of dirty pages in the dirty bitmap, we propose a fast dirty bitmap scanning method to locate the dirty pages, and take a multi-threading data comparison mechanism to locate the real dirty data in one page. The experimental results show that compared with Xen's default system-level checkpointing algorithm, FITDOC can on average reduce checkpointing time 70.54 % with a 1 GB memory size A preliminary version containing some of the results in this paper has been published in the CSE 2014. 123Y. Du et al. and achieve better improvement for VMs with larger memory configurations. FITDOC can reduce the size of checkpointing data 52.88 % on average compared with Remus's incremental solution, which is in page granularity. Compared with the default dirty bitmap scanning method in Xen, the scanning time of FITDOC is decreased by 91.13 % on average.

Reliability and high availability in cloud computing environments: a reference roadmap

“…The checkpointing approach has attracted significant attention over the recent years in the context of fault tolerance research like studies that have been carried out by [107][108][109][110]. Generally, the checkpoint technique periodically saves the state of an application.…”