Data placement schemes in replicated mirrored disk systems

In the present paper, we study the most frequent data placement schemes, i.e., the organ-pipe and camel arrangements, in a mirrored disk system which supports cylinder replication at appropriate locations across the disk surface. Five schemes are proposed to identify the appropriate replica positions for the most frequently accessed cylinders. Three schemes, which are called Left, Right and Symmetric Replication Techniques, are based on an analytical approach. More speci®cally, given a single replica in the above strategies, estimates are derived for the expected seek distance decrease with respect to a non-replicated mirrored disk system. On the other hand, the remaining two schemes, which are called Positional and Frequency Replication Techniques, are based on heuristic approaches. We globally compare the performance of these ®ve schemes as a function of the number of replicas. These results are also compared with the corresponding metrics of a conventional (with no replication) mirrored disk system. Ó 2000 Elsevier Science Inc. All rights reserved.