International Business Machines Corporation

Andrea Sipka

John P Wilkinson

Florent Rostagni

A computer-implemented method, according to one embodiment, includes: sending existing data to a secondary storage volume in a secondary system from a primary storage volume in a primary system. Moreover, in response to receiving a write request at the primary system: a determination is made as to whether existing data corresponding to the write request has already been copied to the secondary storage volume. The write request is performed at the primary system in response to determining that all the existing data corresponding to the write request has already been copied to the secondary storage volume. However, at least a portion of the existing data corresponding to the write request is read from the primary storage volume in response to determining that at least a portion of the existing data corresponding to the write request has not already been sent to the secondary storage volume.

Point-in-time copy on a remote system

A method for improving latency in storage systems, the method comprising, receiving one or more write commands from a host. Determining that one or more bits are not set for a grain associated to a write. Responsive to determining the one or more bits are not set for the grain associated to the write, sending a message to node M requesting node M to set the one or more bits for the grain associated to the write, requesting write data be transferred from the host. Transferring write data from the host. Submitting the write data to a local storage. Replicating the write data to a remote system and complete a write to the host, and notifying node M to clear the one or more bits for the write after a predetermined delay.

Optimized locking for replication solutions

A method and apparatus for validating operation of a data volume on a storage medium. A data integrity component is provided which writes data blocks to the volume in a sequence, each data block storing a sequence number and also write status information specifying the sequence numbers of those preceding data blocks in the stream which are still being written to the volume at the time the data block is generated. Data validation is performed by reading back the stored data blocks from the volume and checking that the sequence numbers stored in them match those that should be present based on the sequence numbers stored in the write status information of the last-written data block found on the volume.

Checking data integrity of data storage systems

A computer-implemented method, according to one embodiment, includes: receiving data at a secondary storage volume from a primary storage volume. In response to receiving a read request: a request is sent for at least a portion of the data corresponding to the read request in response to determining that at least a portion of the data corresponding to the read request is not in any of the regions in the secondary storage volume. The at least a portion of the data corresponding to the read request is received, and further stored in one or more regions in the secondary storage volume. Furthermore, a message is sent indicating that the one or more regions in the secondary storage volume in which the data was stored contain the at least a portion of the data corresponding to the read request received, the message being for updating a primary record.

A computer-implemented method, according to one embodiment, includes: receiving existing data at a secondary storage volume in a secondary system from a primary storage volume in a primary system. In response to receiving a write request at the secondary system: a determination is made as to whether data corresponding to the write request will fully overwrite one or more of the regions in the secondary storage volume. A request is sent to the primary system for existing data corresponding to the secondary storage volume in response to determining that the data corresponding to the write request will not overwrite a portion of a region in the secondary storage volume. The requested existing data is received, and merged with the data corresponding to the write request. The merged data is further written to the one or more respective regions in the secondary storage volume.

A computer program product, according to one embodiment, includes a computer readable storage medium having program instructions embodied therewith. The computer readable storage medium is not a transitory signal per se. Moreover, the program instructions readable and/or executable by a processor to cause the processor to perform a method which includes: maintaining, by the processor, a cascaded mapping relationship at a secondary system. The cascaded mapping relationship extends between the secondary system and a remote primary system. Furthermore, maintaining the cascaded mapping relationship includes: in response to receiving a remote point-in-time copy from the remote primary system, inserting, by the processor, the received remote point-in-time copy immediately downstream from an interface of the cascaded mapping relationship between the secondary system and the remote primary system; and inserting, by the processor, each local point-in-time copy of a storage volume in the secondary system immediately downstream from the storage volume.

Multiple point-in-time copies on a remote system

A computer program product, according to one embodiment, includes a computer readable storage medium (which is not a transitory signal per se) having program instructions embodied therewith which are readable and/or executable by a processor to cause the processor to perform a method which includes: receiving data at a secondary storage volume in a secondary system from a primary storage volume in a primary system. Upon receiving a read request at the secondary system, the method includes: reading the requested data from the secondary storage volume; sending a request to the primary system for the requested data after determining that it is not in the secondary storage volume; receiving the data from the primary system; supplying the requested data; storing the data received from the primary system in the secondary storage volume; updating a secondary record; and sending a message to the primary system for updating a primary record.

A method to efficiently synchronize a secondary volume with a primary volume includes maintaining a primary volume on a primary storage system and creating a copy of the primary volume. Ancestry information is maintained for the primary volume and copy. The copy and associated ancestry information are physically transported from the primary storage system to a secondary storage system. The copy is loaded into a secondary volume of the secondary storage system and the ancestry information of the copy is imported into the secondary volume. The ancestry information is then analyzed to determine if the primary volume and secondary volume share common ancestry. If so, the ancestry information is analyzed to determine differences between the primary volume and the secondary volume. The secondary volume is then synchronized with the primary volume to reconcile the differences. A corresponding system and computer program product are also disclosed.

Self-describing volume ancestry for data synchronization

A multi-node data storage system comprises a first data storage system having an owner node and a backup node in a first location coupled to a second data storage system having an owner node and a backup node in a second location. Each storage system includes a copy of the same data volume. A failure of a node of the multi-node storage system is detected. An outstanding write request to the first storage system is identified. If the owner node in the first storage system fails, it is determined whether the outstanding write corresponds to a host write to the backup node of the first storage system. If so, a retransmission message is sent to the second storage system. Otherwise, the data region associated with the outstanding write request is read from the first storage system, and a resynchronization message is sent to the second storage system.

Handling node failure in multi-node data storage systems

Storage sites are allocated pairs of nodes in which one node of the pair acts as an owner node while the other a backup node. When a local owner node receives a colliding write, the local owner node obtains a lock on the modified database and transfers both the write data and metadata to a remote owner node. The remote owner node returns a write complete message and the local site owner unlocks the modified database. When a local backup node receives a colliding write, the local backup node requests a lock from the local owner node and sends the write data to the remote owner node while the local owner node sends the write metadata to the remote owner node. The remote owner node then returns a write complete message to the local backup node which then requests the modified database be unlocked by the local owner node.

Growing community of inventors

Chandlers Ford, United Kingdom

Andrea Sipka