Patent ID: 8484414
Filing Date: 2013-07-09
Classification: G06F,G11C

Abstract:
1. A storage system comprising: a plurality of first flash memory drives configuring a first RAID group and a plurality of second flash memory drives configuring a second RAID group; and a storage controller coupled to a host computer and the first and the second drives; wherein each of the first and the second flash memory drives includes a drive controller and a storage area, the storage area comprising a plurality of physical blocks, each of the physical blocks comprising a plurality of pages, the drive controller allocating a part of the physical blocks to a plurality of logical blocks provided by the drive controller, managing an unallocated part of the physical blocks as free blocks, executing a read or write process to respective pages of the allocated physical blocks, erasing all of the pages of one of the physical blocks when the one of the physical blocks is unmapped from the logical block, and; wherein the storage controller provides to the host computer, a logical unit configured by a plurality of logical chunks, manages a plurality of physical chunks, each of the physical chunks configured by ones of the logical blocks of either one of the first or the second RAID groups, and allocates one of the physical chunks to one of the logical chunks in response to a write operation addressed within the one of the logical chunks; wherein if a write error has occurred in a write operation addressed in a first one of the physical chunks configured by the ones of the logical blocks of the first RAID group due to a shortage of free blocks in one or more of the first flash memory drives, the storage controller is configured to migrate data from the first one of the physical chunks to a second one of the physical chunks configured by ones of the logical blocks of the second RAID group, allocate the second one of the physical chunks to one of the logical chunks where the first one of the physical chunks has been allocated and send an instruction to unmap the first one of the physical chunks to the first flash memory drives, and wherein each of the drive controllers of the first flash memory drives receiving the instruction to unmap the first one of the physical chunks are configured to unmap the respective storage area corresponding to the logical blocks configuring the first one of the physical chunks.