Increasing the capacity of RAID5 by online gradual assimilation

Disk arrays level 5 (RAID5) are very commonly used in many environments. This kind of arrays has the advantage of parallel access, fault tolerance and little waste of space for redundancy issues. Nevertheless, this kind of storage architecture has a problem when more disks have to be added to the array. Currently, there is no simple, efficient and on-line mechanism to add any number of new disks (not replacing them), and this is an important drawback in systems that cannot be stopped when the storage capacity needs to be increased. We propose an algorithm to add N disks to an array while it continues running. The proposed algorithm for a gradual assimilation of disks has three major advantages: it has an easily controlled overhead, it allows the user to benefit from the higher parallelism achieved by the part of the array that has already been converted, and finally, it can be used in 7/24 systems.