Abstract: 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.

Abstract: Various systems, processes, and products may be used to manage remote data replication. In particular implementations, a system and process for managing remote data replication may include the ability to store versions of a disk at a first site, a second site, and a third site. The version of the disk at the first site may store input/output for a host system, the version at the second site may be a synchronous replication of the version at the first site, and the third site may be an asynchronous replication of the version at the first site. The system and process may also include the ability to synchronize the version at the first site with the version at the third site if the second site is unavailable.

Abstract: Various systems, processes, and products may be used to manage remote data replication. In particular implementations, a system and process for managing remote data replication may include the ability to store versions of a disk at a first site, a second site, and a third site. The version of the disk at the first site may store input/output for a host system, the version at the second site may be a synchronous replication of the version at the first site, and the third site may be an asynchronous replication of the version at the first site. The system and process may also include the ability to synchronize the version at the first site with the version at the third site if the second site is unavailable.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Embodiments of the present invention disclose a method, a computer program product, and a computer system for data synchronization. A first data storage device reads a first data region and generates a first hash of the first data region before transmitting the first hash to a second data storage device. The second data storage device reads a second data region corresponding to the first data region and generates a second hash of the second data region. The second data storage device then determines whether the first hash matches the second hash and, based on determining that the first hash does not match the second hash, transmits data of the second data region to the first data storage device. The first data storage device applies the data of the second data region, thereby synchronizing the first data storage device and the second data storage device.

Abstract: Inventive systems, techniques, and program products for copy-on-read, particularly in the context of disaster recovery (DR), are described. The inventive concepts include: a primary system for copy-on-read processing and disaster recovery, the primary system comprising: a primary storage volume available at a primary system, the primary storage volume storing one or more data portions; a record of regions of the primary storage volume, wherein a given region of the primary storage volume is marked when a given data portion stored on the primary storage volume is sent to a disaster recovery system; and a record monitoring component configured to determine whether one or more later writes to marked region(s) of the primary storage volume should be immediately replicated to the disaster recovery system, wherein the later writes occur after replicating the given data portion stored on the primary storage volume to the disaster recovery system.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A mechanism is provided for replicating data in a data storage system that comprises a first data storage device, a second data storage device, and a third data storage device arranged to receive write requests from the first data storage device and second data storage device. The first data storage device or the second data storage device is selected using a characteristic of the first data storage device and the second data storage device. The first data storage device receives a first write request and sends the first write request to the second data storage device, and the second data storage device receives a second write request and sends the second write request to the first data storage device. The data storage device selected using the characteristic sends a write request to the third storage device in response to a notification the non-selected data storage device has completed the update.

Abstract: 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.

Abstract: Method and system are provided for predictive point-in-time copy for storage systems. The method may include: recording a frequency of writes to an area of a storage volume; and prioritising areas for having point-in-time copies carried out based on the write frequency to an area, wherein areas in the storage volume having a high write frequency are prioritised before areas with a lower write frequency. An area may be of a coarser granularity than a region tracked for the point-in-time copy. The method may include: recording the frequency of writes to an area in a given period; and prioritising areas by their frequency of writes in the given period immediately prior to the point-in-time copy.

Abstract: 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.

Abstract: Various systems, processes, and products may be used to manage remote data replication. In particular implementations, a system and process for managing remote data replication may include the ability to store versions of a disk at a first site, a second site, and a third site. The version of the disk at the first site may store input/output for a host system, the version at the second site may be a synchronous replication of the version at the first site, and the third site may be an asynchronous replication of the version at the first site. The system and process may also include the ability to synchronize the version at the first site with the version at the third site if the second site is unavailable.

Abstract: Embodiments of the present invention disclose a method, a computer program product, and a computer system for data synchronization. A first data storage device reads a first data region and generates a first hash of the first data region before transmitting the first hash to a second data storage device. The second data storage device reads a second data region corresponding to the first data region and generates a second hash of the second data region. The second data storage device then determines whether the first hash matches the second hash and, based on determining that the first hash does not match the second hash, transmits data of the second data region to the first data storage device. The first data storage device applies the data of the second data region, thereby synchronizing the first data storage device and the second data storage device.

Abstract: Various systems, processes, and products may be used to manage remote data replication. In particular implementations, a system and process for managing remote data replication may include the ability to store versions of a disk at a first site, a second site, and a third site. The version of the disk at the first site may store input/output for a host system, the version at the second site may be a synchronous replication of the version at the first site, and the third site may be an asynchronous replication of the version at the first site. The system and process may also include the ability to synchronize the version at the first site with the version at the third site if the second site is unavailable.

Abstract: 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.