Abstract:

Due to the bandwidth restriction and the long delay of IP network, iSCSI initiator and iSCSI target have to wait for a longer time until they acknowledge the status or the control command sent by the other party. The communication of iSCSI protocol takes a large part of the total cost. Therefore, the cache data's loading cost of iSCSI storage is different from the traditional direct attached storage. The existing researches focused on achieving high cache hit ratios, but rarely paid attention to reducing the loading cost of miss data for improving the storage system performance. In the paper, a cache replacement algorithm called CFL-LRU (LRU Combined with Frequency and data Length) was proposed for iSCSI storage. The algorithm not only considers the time and the frequency but also takes into account the logical block address continuity of pages, thereby compromising the hit rate and the miss penalty. Our tracedriven simulation results show that, for different kinds of workloads and cache size, the CFL-LRU outperforms the others.

Key words: iSCSI;network storage;replacement algorithm;hit ratio;miss penalty