Research On Cache Mirroring Technology Of Dual Controller Disk Array

With the rapid development of information technology, the importance and value ofinformation continuous growth, consequently, higher requirements of reliability andavailability of the storage system are emphasized. Currently, the disk array has become thebasic unit in large-scale storage systems; as the core component of a disk array, thediskarray controller’s performance directly determines the overall performance of the diskarray. Therefore, to design a disk array controller with high reliability and availability hasbecome a hot research topic in the storage system field.Cache is designed by allocating an area from the memory of the dual-controller.EachCache block consist of a physical page frame.The Cache blocks are organized in somelogical structure as radix tree,meanwhile reading and writing Least-Recently-Used lists arecreated for Cache scheduling.Additional memory area is allocated for the mirror Cachespace,Cache blocks from which are also organized into radix tree. In consideration of costand portability,mirror data synchronized transmission via kernel socket interface functionsis a proper method. Data mirroring strategy is focus on the size of the dirty data (spatiallocality) and the update frequency of the same Cache block (temporal locality),respectively,and the mirror synchronization mechanisms based on the size of the data andthe time interval have been completed.The Cache block-based data mirroring functionmodule has been implemented upon the device handle layer of iSCSI target middle layerSCST (SCSI Target mid-level).Several kinds of experiments have been conducted on the dual-controller disk array.The test results show that the I/O performance of the disk array with Cache has beenimproved to some extent, and the dirty data isn’t lost when one of the dual controller cameto fail which means the reliability is enhanced.