网络磁盘阵列流水调度研究

Research on Network RAID Pipeline Technology

存储系统采用流水处理技术有两个前提条件:(1)在前一个 I/O命令没有完全结束之前,系统能获取下一个I/O命令的有关信息;(2)不同部件应能同时操作,资源不发生冲突.网络磁盘阵列满足这两个条件,可以在 I/O调度过程中采用流水处理技术.根据 I/O调度进程的重叠度,流水调度方式可以分为固定流水方式和柔性流水方式.在固定流水方式中,多进程按照固定的重叠方式执行;而在柔性流水方式中,则通过判断进程的完成顺序,在一定程度上自由组合多个进程进行重叠.实验结果证明,在多用户进程的条件下,两种流水调度方式都能提高网络磁盘阵列的带宽利用率.

Storage system should meet two requirements to use pipeline technology, one is that the system can get information of next command before the completion of current command, and the other is that different units can operate simultaneously without conflict of different resources. Meeting these two requirements, network RAID can use pipeline operation during I/O scheduling. According to overlap degree of I/O scheduling processes, pipeline operation of network RAID can be divided into two methods, one is fixed pipeline scheduling, and the other is flexible pipeline scheduling. Multi processes will execute by fixed scheduling sequence in fixed pipeline scheduling. Otherwise, flexible pipeline scheduling judges the completing sequence and overlaps multi processes freely. Tests prove that the above two kinds of pipeline scheduling can improve bandwidth utilization when a lot of clients access network RAID.