Striping on Hierarchical Storage Systems

The data striping technique has been successfully applied on disks to reduce the time to access objects from the disks as shown in Chapter VI. Similarly, the striping technique has been investigated to reduce the time to access objects from the tape libraries. Similar to the striping on disks, the objective of the parallel striping method is to reduce the time to access objects from the tape libraries. The parallel tape striping directly applies the striping technique to place data stripes on tapes. The triangular placement method changes the order in which data stripes are stored on tapes to further enhance the performance. In the next section, the parallel tape striping method will be described. The performance of the parallel tape striping follows. After that, the triangular placement method is explained, and it is followed by the performance of the triangular placement method.

Striping on Disks

Multimedia streams need continuous data supply. The aggregate data access requirement of many multimedia streams imposes very high demand on the access bandwidth of the storage servers. The disk striping or data striping methods spreads data over multiple disks to provide high aggregate disk throughput (Chua, Li, Ooi, & Tan, 1996; Hsieh, Lin, Liu, Du, & Ruwart, 1995). In addition to the popularity of multimedia objects that we have described in the last chapter, multimedia streams consume an object in a sequential manner. The striping methods make use of this access pattern to evenly spread the workload across disks. This can increase aggregate disk throughput so that high bandwidth streams can be delivered continuously. We first describe the simple striping method that places data stripes on a set of disks in the next section. After that, the staggered striping method that places data on a set of disks in a rotating manner is described. The pseudorandom placement method that stores data stripes on random disks is explained before we summarize this chapter.