Fujitsu Corporation

Tomoyuki Suganuma

Suijin Takeda

Mikio Itoh

Hirofumi Morita

When an amount of write data instructed by an upper-level system is small, a plurality of disk units are accessed individually and data split in sectors is written therein (Level 5 RAID). When an amount of write data instructed by the upper-level system is large, the plurality of disk units are accessed in parallel and data split in sectors is written therein (Level 3 RAID). When a disk unit in an array, to which a setup instruction is issued according to a processing request sent from the upper-level system, returns a fault reply, an ID management table is used to allocate an auxiliary disk instead of the failing disk unit. After the allocation, data is restored to the replacement disk using the data in normal disk units in the same rank. In a dual-port access configuration, when two transactions access disk units connected to the same port, a deadlock may occur depending on the access procedure. It is checked if the conditions for a deadlock are established, so that access will be obtained according to a procedure for preventing or avoiding a deadlock.

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Kawasaki, Japan

Tomoyuki Suganuma