Hitachi, Ltd.

Hitachi Computer Engineering Co., Ltd.

Yoshiaki Muto

Hisaharu Takeuchi

Katsunori Nakamura

Shigeru Kishiro

Yoshiro Shiroyanagi

Kazunari Miyachi

Tomohito Ogino

Upon receiving an access request from a server, a microprocessor allocates a free slot as a data storage destination that is different from the LU# and LBA designated as a storage destination of user data, stores user data and data identifying information for identifying the user data in the free slot, and zero-clears the pre-updated data slot designated with the LU# and LBA. During a subsequent read access, the microprocessor accesses the data slot and, if the read data identifying information and the data identifying information designated in the read access from the server coincide, transfers this read data to the server as correct data, and, if the read data identifying information and the data identifying information designated in the read access from the server do not coincide, performs processing for recovering correct data based on the read data identifying information.

Storage apparatus

A storage apparatus is provided in which the data amount of transfer data to a secondary disk controller from a primary disk controller at the event of remote copying can be reduced, and data integrity also can be assured. According to the storage apparatus, in the primary disk controller, overwriting update data in same records during a specified time between a preset first base point and a preset second base point on the update data that are stored in the second area of the cache memory and that are to be transferred to the secondary disk controller; and in the secondary disk controller, handling the update data between the first base point and the second base point as real data having consistency.

Storage apparatus for asynchronous remote copying

In a storage system allowing redundant writing, a technology is provided capable of achieving control including efficient return to redundancy while reducing load on a host and trouble for a user. The host performs the redundant writing of data into data volumes in primary and secondary storage apparatuses. Each storage apparatus retains information including update data from the host as a journal (update data history information). When one of two systems for redundant writing is in a failed state and it is to be returned to a redundant state, the storage apparatuses communicate with each other regarding the journals not through the host. A retained portion of the journal of the normal system after the latest synchronization point required for synchronizing the volumes is transferred through data copy to the system to be recovered. Based on the transferred portion of the journal, the volume is restored and synchronized.

Storage system, redundancy control method, and program

When recording records into the IC memory group of a magnetic disk subsystem the records being composed of a count area of a fixed length, key area of a variable length and a data area of a variable length, data of a special format which is judged by ECC check to be an abnormal data is written at the top of the count area in each record. When reading an object record from the IC memory group, it is judged by ECC check whether or not the read data is an abnormal one. When the read data is judged to be an abnormal one, the read data is compared with the data of special format, and when there is found a coincidence between them, it is recognized that the read data are at the top of the count area. When writing data, data which are judged by ECC check to be a normal are suffixed to data which are judged by ECC check to be abnormal. When the read data are judged by the ECC check to be abnormal and judged by a next ECC check to be normal, it is recognized that the read data are at the top of the count area.

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Odawara, Japan

Yoshiaki Muto