Architecture and Performance Potential of STICS SCSI-To-IP Cache Storage

Data storage plays an essential role in today’s fast-growing data-intensive network services. New standards and products emerge very rapidly for networked data storages. Given the mature Internet infrastructure, overwhelming preference among IT community recently is using IP for storage networking because of economy and convenience. iSCSI is one of the most recent standards that allows SCSI protocols to be carried out over IP networks. However, there are many disparities between SCSI and IP in terms of speeds, bandwidths, data unit size, and design considerations that prevent fast and efficient deployment of SAN (Storage Area Network) over IP. This paper introduces STICS (SCSI-To-IP Cache Storage), a novel storage architecture that couples reliable and highspeed data caching with low-overhead conversion between SCSI and IP protocols. A STICS block consists of one or several storage devices such as disks or RAID, and an intelligent processing unit with CPU and RAM. The storage devices are used to cache and store data while the intelligent processing unit carries out caching algorithm, protocol conversion, and self-management functions. Through efficient caching algorithm and localization of certain unnecessary protocol overheads, STICS can significantly improve performance, reliability, manageability, and scalability over current iSCSI systems. Furthermore, STICS can be used as a basic plug-and-play building block for data storage over IP. Analogous to “cache memory” invented several decades ago for bridging the speed gap between CPU and memory, STICS is the first-ever “cache storage” for bridging the gap between SCSI and IP making it possible to build efficient SAN over IP. We have carried out a partial implementation and simulation experiments to study the performance potential of STICS. Numerical results using popular PostMark benchmark program and EMC’s trace have shown dramatic performance gain over the iSCSI implementation.