容许两个盘故障的磁盘阵列数据布局与图分解的条件和存在性研究

从一个新的途径讨论容许两个盘故障的磁盘阵列数据布局：把由数据单元和通过“异或”运算得到的校验单元组成的校验组用一个图表示，把校验组容许两个盘故障的阵列布局归结为校验组的单元集合的划分，进而转化为校验组的图的顶点和边组成集合的满足一定条件的分解．证明了校验组容许两个盘故障的单元集合划分的充分必要条件及存在性；讨论了优化阵列布局方案性能的条件；给出了阵列布局的步骤．从而为设计具有最优性能的容许两个盘故障的磁盘阵列数据布局方案提供了有效的途径．

The Study of Graph Decompositions and Placement of Parity and Data to Tolerate Two Failures in Disk Arrays: Conditions and Existance

A novel method for tolerating up to two disk failures in disk arrays has been presented. By representing a check group consisting of date and parity units with a graph, the conditions for tolerating two disk failures in disk arrays becomes to that of partitions of check group, and thus to that of the decompositions of its graph. A necessary and sufficient condition for the partition of check group is proved; the existence of the partition is given; the condition for optimizing the performance of the placement scheme is discussed; and the step of placement of the date and parity in a disk array is shown. It presents an efficient method for placement schemes with optimizing performance to tolerating two disk failures in disk arrays.