Abstract: A computer-implemented method according to one embodiment includes identifying a block size used by an application, where the block size is a power of two, constructing, utilizing a plurality of instances of a first array code, a single instance of a second array code having a symbol size that matches the block size used by the application, where the symbol size of the second array code is always a power of two, and implementing the second array code within the application.

Abstract: A computer-implemented method according to one embodiment includes identifying a block size used by an application, where the block size is a power of two, constructing, utilizing a plurality of instances of a first array code, a single instance of a second array code having a symbol size that matches the block size used by the application, where the symbol size of the second array code is always a power of two, and implementing the second array code within the application.

Abstract: A computer-implemented method, apparatus, and computer program product implemented in a storage system are disclosed. The storage system comprises a plurality of virtual storage nodes and a plurality of block storages. Each of the block storages is attached to a single virtual storage node. One or more processors receive an availability for the plurality of virtual storage nodes from at least one virtual storage node. In response to receiving the availability for the plurality of virtual storage nodes, the one or more processors determine one or more virtual storage nodes are unavailable. In response to determining one or more virtual storage nodes are unavailable, the one or more processors cause a representative node of the plurality of virtual storage nodes to redistribute one or more block storages attached to one or more unavailable virtual storage nodes to one or more available virtual storage nodes.

Abstract: Systems, computer program products, and methods that can integrate resources at a disaster recovery site are provided. One method includes generating, on a primary site, a set of storage snapshots based on combining another set of storage snapshots and incremental changes to mirrored data on a backup site in which the storage snapshots include a second snapshot format utilized on the backup site. The method further includes converting the set of storage snapshots from the second snapshot format to a first snapshot format utilized on the primary site to generate a yet another set of storage snapshots and converting, on the backup site, a set of storage snapshots including the incremental changes and the second snapshot format to the first snapshot format to generate still another set of eighth storage snapshots. The storage snapshots on both sites represent the same data in the same snapshot format without bulk data transfer.

Abstract: Systems, computer program products, and methods that can integrate resources at a disaster recovery site are provided. One method includes generating, on a primary site, a set of storage snapshots based on combining another set of storage snapshots and incremental changes to mirrored data on a backup site in which the storage snapshots include a second snapshot format utilized on the backup site. The method further includes converting the set of storage snapshots from the second snapshot format to a first snapshot format utilized on the primary site to generate a yet another set of storage snapshots and converting, on the backup site, a set of storage snapshots including the incremental changes and the second snapshot format to the first snapshot format to generate still another set of eighth storage snapshots. The storage snapshots on both sites represent the same data in the same snapshot format without bulk data transfer.

Abstract: Data migration from a source data storage system to a target data storage system, where the source and target data storage systems are of two different types, using a virtual file system to store the data at the target data storage system, with the target data storage system being configured to store data in the manner of the source data storage system. In some embodiments, more convenient and efficient data migration can be provided without changing the architecture of an existing data storage system as far as possible.

Abstract: A method implemented in a computer infrastructure having computer executable code tangibly embodied on a computer readable medium. The computer executable code is operable to dynamically adjust quorum requirements for a voting set V of a server cluster, including a plurality of servers, to ensure that a response of the server cluster to a client request remains Byzantine fault tolerant when at least one of: a failed server of the server cluster is replaced with at least one new server, such that a total set S of servers that have ever been members of the server cluster is increased, and an existing server is removed from the voting set V.

Abstract: Methods and apparatus are provided for copying data from a primary storage facility to a secondary storage facility which reduce the workload on the storage controller in the primary facility and minimize bandwidth usage. The primary storage facility includes a primary data replication appliance which transfers data to a secondary replication appliance. Updated data from a host is both stored through a storage controller in the primary facility and also received by the primary replication appliance. Logic in the primary replication appliance determines whether the immediately previous version of the data is in a buffer from a previous storage operation. If so, the current (updated) version of the data is compared with the previous version and the difference, such as calculated through a bit-wise exclusive-OR operation, is transferred to the secondary replication appliance.

Abstract: An apparatus, method and computer program operable in a network controls consistency guarantees of a plurality of data copies in a storage apparatus, and includes: a lease control component for extending a lease to the storage apparatus; and a consistency freeze/thaw component responsive to a failure indication for initiating a consistency freeze action at the storage apparatus prior to expiration of the current group lease period. It may further include a timer component for waiting the apparatus for a predetermined period after the consistency freeze action, where the consistency freeze/thaw component is operable to initiate a thaw action at the storage apparatus.

Abstract: A method implemented in a computer infrastructure having computer executable code tangibly embodied on a computer readable medium. The computer executable code is operable to dynamically adjust quorum requirements for a voting set V of a server cluster, including a plurality of servers, to ensure that a response of the server cluster to a client request remains Byzantine fault tolerant when at least one of: a failed server of the server cluster is replaced with at least one new server, such that a total set S of servers that have ever been members of the server cluster is increased, and an existing server is removed from the voting set V.

Abstract: A replicated state machine includes multiple state machine replicas. In response to a request from a client, the state machine replicas can execute a service for the request in parallel. Each of the state machine replicas is provided with a request manager instance. The request manager instance includes a distributed consensus means and a selection means. The distributed consensus means commits a stimulus sequence of requests to be processed by each of the state machine replicas. The selection means selects requests to be committed to the stimulus sequence. The selection is based on an estimated service time of the request from the client. The estimated service time of the request from the client is based on a history of service times from the client provided by a feedback from the state machine replicas. As such, requests from multiple clients are serviced fairly.

Abstract: A method implemented in a computer infrastructure having computer executable code tangibly embodied on a computer readable medium. The computer executable code is operable to dynamically adjust quorum requirements for a voting set V of a server cluster, including a plurality of servers, to ensure that a response of the server cluster to a client request remains Byzantine fault tolerant when at least one of: a failed server of the server cluster is replaced with at least one new server, such that a total set S of servers that have ever been members of the server cluster is increased, and an existing server is removed from the voting set V.

Abstract: A method, storage system, and machine-readable medium for resynchronizing data stored among a first storage element and a second storage element of a remote copy pair of storage elements is disclosed. According to one embodiment, a method is provided which includes detecting a reestablishment of a remote copy relationship between the first and second storage elements and performing a resynchronization operation in response to this detection. Performing the resynchronization operation comprises transmitting data of a second change record associated with the second storage element to the first storage element, combining the second change record with a first change record associated with the first storage element, identifying a data segment of the second storage element utilizing the combined change record, and overwriting data of the first storage element with data of the identified data segment.

Abstract: A method implemented in a computer infrastructure having computer executable code tangibly embodied on a computer readable medium. The computer executable code is operable to dynamically adjust quorum requirements for a voting set V of a server cluster, including a plurality of servers, to ensure that a response of the server cluster to a client request remains Byzantine fault tolerant when at least one of: a failed server of the server cluster is replaced with at least one new server, such that a total set S of servers that have ever been members of the server cluster is increased, and an existing server is removed from the voting set V.

Abstract: A method, storage system, and machine-readable medium for resynchronizing data stored among a first storage element and a second storage element of a remote copy pair of storage elements is disclosed. According to one embodiment, a method is provided which includes detecting a reestablishment of a remote copy relationship between the first and second storage elements and performing a resynchronization operation in response to this detection. Performing the resynchronization operation comprises transmitting data of a second change record associated with the second storage element to the first storage element, combining the second change record with a first change record associated with the first storage element, identifying a data segment of the second storage element utilizing the combined change record, and overwriting data of the first storage element with data of the identified data segment.

Abstract: A method, storage system, and machine-readable medium for resynchronizing data stored among a first storage element and a second storage element of a remote copy pair of storage elements is disclosed. According to one embodiment, a method is provided which includes detecting a reestablishment of a remote copy relationship between the first and second storage elements and performing a resynchronization operation in response to this detection. Performing the resynchronization operation comprises transmitting data of a second change record associated with the second storage element to the first storage element, combining the second change record with a first change record associated with the first storage element, identifying a data segment of the second storage element utilizing the combined change record, and overwriting data of the first storage element with data of the identified data segment.

Abstract: A replicated state machine includes multiple state machine replicas. In response to a request from a client, the state machine replicas can execute a service for the request in parallel. Each of the state machine replicas is provided with a request manager instance. The request manager instance includes a distributed consensus means and a selection means. The distributed consensus means commits a stimulus sequence of requests to be processed by each of the state machine replicas. The selection means selects requests to be committed to the stimulus sequence. The selection is based on an estimated service time of the request from the client. The estimated service time of the request from the client is based on a history of service times from the client provided by a feedback from the state machine replicas. As such, requests from multiple clients are serviced fairly.

Abstract: A replicated state machine includes multiple state machine replicas. In response to a request from a client, the state machine replicas can execute a service for the request in parallel. Each of the state machine replicas is provided with a request manager instance. The request manager instance includes a distributed consensus means and a selection means. The distributed consensus means commits a stimulus sequence of requests to be processed by each of the state machine replicas. The selection means selects requests to be committed to the stimulus sequence. The selection is based on an estimated service time of the request from the client. The estimated service time of the request from the client is based on a history of service times from the client provided by a feedback from the state machine replicas. As such, requests from multiple clients are serviced fairly.