Abstract: The SCSI commands (XDWRITE, XDREAD and XPWRITE) are already on fibre channel drives to involve the drives participating in performing RAID 5 XOR functions. For “small writes”, traditional RAID-5 implementation requires a host or a RAID controller to read the original parity block, then construct the new parity block by computing the exclusive-or (XOR) of the original parity block and data blocks. the new SCSI commands have been adopted to implement the “small writes” without reading the parity block, and cause the drive to construct and update the parity block itself. By utilizing the disk’s XOR engine, the throughput is increased and the average latency is also reduced.

Key words: RAID, Small write, Exclusive-or engine, Disk array

摘要： SCSI标准中已扩充了新的SCSI命令(XDWRITE，XDREAD，XPWRITE等)，用以实现高效RAID-5写操作。对“小写”操作，传统的方法需要主机或RAID控制器读入原有的校验块，通过异或计算来构造新的校验块。采用这些新的SCSI命令实现“小写”操作，不再需要读入校验块，由磁盘来进行异或运算构造出校验块。利用磁盘的异或引擎，提高了RAID-5的吞吐率，缩短了平均响应时间。

关键词: RAID, 小写, 异或引擎, 磁盘阵列

CLC Number: 

• TP393.08