Distributing Orthogonal Redundancy on Adaptive Disk Arrays

When upgrading storage systems, the key is migrating data from old storage subsystems to the new ones for achieving a data layout able to deliver high performance I/O, increased capacity and strong data availability while preserving the effectiveness of its location method. However, achieving such data layout is not trivial when handling a redundancy scheme because the migration algorithm must guarantee both data and redundancy will not be allocated on the same disk. The Orthogonal redundancy for instance delivers strong data availability for distributed disk arrays but this scheme is basically focused on homogeneous and static environments and a technique that moves overall data layout called re-striping is applied when upgrading it. This paper presents a deterministic placement approach for distributing orthogonal redundancy on distributed heterogeneous disk arrays, which is able to adapt on-line the storage system to the capacity/performance demands by only moving a fraction of data layout. The evaluation reveals that our proposal achieve data layouts delivering an improved performance and increased capacity while keeping the effectiveness of the redundancy scheme even after several migrations. Finally, it keeps the complexity of the data management at an acceptable level.