Optimizating The IO Performance Based On Metadata Compression In ISCSI Environment

The maturity, scalability and affordability of TCP/IP internet have made the fusion of TCP/IP internet and storage system become one of the most attractive scheme in small and medium storage system. i SCSI(internet Small Computer System Interface) is a network storage standard which is developed by the IEETF in order to connect storage devices with IP protocol.As the development of the iSCSI technology, iSCSI has been widely used in various scenes. Synchronous metadata writes ocucupy a large proportion in MailServer-like workload, as the file system and iSCSI system have not been optimized on this data property, iSCSI exhibit poor performance.For the poor performance under iSCSI environment, analyzes the reason that causes the write latency in threes layers respectively, ie, the general block layer, the SCSI layer and the iSCSI layer. Based on the analysis, modifies the general block layer, the SCSI layer and the iSCSI layer, designs and implements an metadata fast transmission scheme based on compression. Specifically, add the operation of distinguishing the metadata writes and compressing them with XOR in general block layer, designs and implements the IO-path which can handle the synchronous metadata write, and modifies the SCSI and ISCSI protocols.The test results show that the proposed optimization for the iSCSI system meets the design objectives. Under the workloads with high proportion of metadata and require synchronization, the optimized system shows about 15% write rate improvement and about 23% write latency decrease. And based on the analysis of the results, found that a trade-off exists between the system write performance and CPU utilization.