The Design And Implementation Of Dual-controller Storage Server’s Cache Module In Inspur

With the rapid development of cloud computing and big data, the Internet companies are pursuing better performance and usability in big data storage. In servers’field, in order to improve usability and avoid interrupts caused by single-point fault in controller, dual-controller storage servers are used in data storage systems.Currently, the speed gap between CPU processing and disk I/O is becoming bigger and bigger, and disk I/O speed has become the bottleneck of the storage servers’performance. To fix this gap, using disk cache in controllers to reduce disk fetching and improve the storage servers’performance. Also, maintaining the synchronization among these two controllers can avoid data lost and service interruption caused by single-controller’s breakdown. Meanwhile, the heartbeat module can monitor the other controller’s status and take over when system’s down, to keep service uninterrupted.In this paper, based on iSCSI Enterprise Target (IET), one open-source softeware of iSCSI controller, we design and implement an independent cache module in dual-controller storage server. This cache module includes standalone cache module and sync module. Standalone cache module implements read, write, write back, etc. and sync module implements the sync process of dirty data in two controllers to keep coherency and avoid data lost. Cache module manages one piece of physical main memory, which is indepent of Linux memory management system. Radix tree is used to rapidlly search. LRU double-linked list is used to replace victim pages. Gigabit NIC is linked directly to provide full-speed channel for sync process.In this work, we design and implement functions in this independent cache module, and multi-thread programming is used to improve performance. Because iSCSI protocol is improved, read and write performance has been fully explored. Using Iometer test tool, read/write speed is compared in dual-controller storage systems with and without cache module. And results demonstrate that this cache module improves storage performance.