Abstract: Peer storage systems share the workload of asynchronously replicating a shared logical storage unit (LSU) to a target system. Peer storage systems (S1 and S2) that synchronously replicate a shared LSU share the workload of asynchronously replicating the shared LSU to a target system (S3) by dividing ownership of the replication cycles in an alternating manner without a strict synchronization of cycles between the peer storage systems. Rather, a given cycle number (e.g., Cycle 1) on S1 may not start and end with a same write operation as a same cycle number (Cycle 1) on S2, such that cycles on S1 (e.g., Cycle 1 and Cycle 2) overlap with cycles having the same number (Cycle 1 and Cycle 2) on S2. S1 may asynchronously replicate to S3 only the cycles it owns, and S2 may asynchronously replicate to S3 only the cycles it owns to S3.

Abstract: Maintaining consistency for asynchronous replication of LUNs of a local storage system to corresponding LUNs of a remote storage system includes copying application data written to LUNs to cache slots, copying metadata of LUNs to cache slots, associating a first sequence number to all metadata modifications and all application data writes that are begun after a first time and before a second time, associating a second sequence number, different from the first sequence number, to all metadata modifications and all application data writes that are begun after the second time, and, after completion of all metadata modifications and all application data writes associated with the first sequence number, initiating transfer to the remote storage system of all metadata modifications and all application data writes associated with the first sequence number. Each cache slot may include a field that indicates a corresponding sequence number.

Abstract: Data may be replicated from a host storage system to a target storage system. It may be determined to replicate a first logical storage element on the source storage system to a second logical storage element on the target storage system, wherein the first logical storage element defines a first data portion having a first value. It may be determined that a third logical storage element on the target storage system defines a second data portion having the first value. The first logical storage element may be replicated to the second logical storage element by establishing a deduplication relationship between the second logical storage element and the third logical storage element on the target storage system without transmitting the first data portion from the source storage system to the target storage system.

Abstract: The system, devices, and methods disclosed herein relate to a dynamic, robust method for choosing a “winner” in an active-active data storage network. In the systems and methods disclosed herein, two or more intelligent nodes within an active-active data storage network periodically exchange operational parameters in an ongoing negotiation regarding who should be the winner in the event of a communication failure within the network. The winner is chosen dynamically based on the operational parameters. A witness is kept apprised of the winner. In the event of a communication failure between the two nodes, the winner is chosen by the witness based on the most recently negotiated lock file reported by one or both of the nodes.

Abstract: The system, devices, and methods disclosed herein relate to a dynamic, robust method for choosing a “winner” in an active-active data storage network. In the systems and methods disclosed herein, two or more intelligent nodes within an active-active data storage network periodically exchange operational parameters in an ongoing negotiation regarding who should be the winner in the event of a communication failure within the network. The winner is chosen dynamically based on the operational parameters. A witness is kept apprised of the winner. In the event of a communication failure between the two nodes, the winner is chosen by the witness based on the most recently negotiated lock file reported by one or both of the nodes.

Abstract: Techniques are described for processing multi-page write operations to maintain write level consistency. A multi-page write spanning multiple cache pages is directed to a target device and received on a first data storage system where writes to the target device are synchronously replicated to a second data storage system. On the first data storage system, each of the multiple cache pages may be synchronously replicated to the second data storage system. A lock on each of the cache pages is not released until an acknowledgement is received regarding successful replication of the cache page. On the second data storage system, requests to replicate the multiple cache pages containing write data of the multi-page write are received and processed using locks of corresponding cache pages on the second data storage system. Such techniques also handle concurrent reads and/or writes. Deadlock detection and resolution processing may be performed for concurrent writes.

Abstract: The system, devices, and methods disclosed herein relate to a dynamic, robust method for choosing a “winner” in an active-active data storage network. In the systems and methods disclosed herein, two or more intelligent nodes within an active-active data storage network periodically exchange operational parameters in an ongoing negotiation regarding who should be the winner in the event of a communication failure within the network. The winner is chosen dynamically based on the operational parameters. A witness is kept apprised of the winner. In the event of a communication failure between the two nodes, the winner is chosen by the witness based on the most recently negotiated lock file reported by one or both of the nodes.

Abstract: Maintaining write consistency between at least two mirrored storage devices includes receiving a write request for a particular block, obtaining a reservation for the particular block, waiting for the particular block to become available in response to not being able to successfully obtain the reservation, writing the particular block in response to successfully obtaining the reservation, and writing the particular block at a remote one of the storage devices following writing the particular block at the particular one of the storage devices. If a retryable indicator is received, the system waits a predetermined amount of time and releases the reservation. The system responds with a success indicator when writing the particular block at a remote one of the storage devices succeeds and responds with a failure indicator when writing the particular block at a remote one of the storage devices fails and the retryable indicator is not received.

Abstract: Described are data replication techniques. Y cycles of writes directed to a first storage device of a first data storage system are collected, Y>2. Each of the Y cycles denotes writes directed to the first storage device at an occurrence of a fixed time interval. Writes of cycle N?1 directed to the first storage device are transmitted from the first data storage system to a second data storage system. Writes of cycle N?2 are applied to a second storage device. An acknowledgement regarding cycle N?1 is sent from the second data storage system to the first data storage system responsive to determining that the writes of cycle N?1 directed to the first storage device have been received by the second data storage system and that the writes of cycle N?2 directed to the first storage device have been applied to the second storage device.

Abstract: Managing reservations for at least two different sites competing for a resource includes maintaining a table of groups of sites, where each group competes for the same resource, one of the different sites requesting a reservation for a particular resource, determining if the reservation is available by consulting the table, denying the reservation to the one of the at least two different sites in response to access having been previously reserved for an other one of the different sites, and granting the reservation to the one of the at least two different sites and reserving access for the one of the at least two different sites in response to the resource being available. The managed resources may correspond to data storage and the two different sites may be mirrored storage devices. In response to a failure of communication between the two different sites, pending writes may be failed.

Abstract: Providing multiple witnesses that manage resources for at least two different sites includes one of the sites choosing a particular one of the witnesses, the one of the at least two different sites confirming that the particular one of the witnesses is available to manage resources, the one of the at least two different sites communicating with other ones of the at least two different sites to determine if the particular one of the witnesses is acceptable to the other ones of the at least two different sites, and choosing the particular one of the witnesses in response to the particular one of the witnesses being available to manage resources and the particular one of the witnesses being acceptable to all of the other ones of the at least two different sites. The managed resources may correspond to data storage and the sites may be mirrored storage devices.

Abstract: Replication of a storage object to a remote storage array is seamlessly maintained by i) while write operations directed to the storage object are being collected into a set of write cycles that are stored in a master storage array, also collecting the write operations directed to the storage volume into a set of write cycles stored in a slave storage array, and ii) in response to detecting a failure of the master storage array, and while the host computer continues to access the storage object using a copy of the storage object located in the slave storage array, transmitting the write cycles stored in the slave storage array to the remote storage array, so that the remote storage array can apply the write operations in the write cycles it receives from the slave storage array on the copy of the storage object contained in the remote storage array.

Abstract: A data storage system provides asymmetric multi-path access to a storage device from a host computer using a storage protocol such as SCSI. Device state information is maintained indicating that one path of set of paths between the host computer and the storage device is a non-fully-functional path. In response to receiving device discovery commands from the host computer on the one path and the one path being indicated to be a non-fully-functional path, the data storage system returns respective good responses indicating that the storage device is accessible to the host computer via the non-fully-functional path. However, in response to receiving a test unit readiness command from the host computer on the one path and the one path being indicated to be a non-fully-functional path, an error response is returned which causes the host computer to select an alternative path of the set of paths for the data transfer.

Abstract: Techniques are described for processing multi-page write operations to maintain write level consistency. A multi-page write spanning multiple cache pages is directed to a target device and received on a first data storage system where writes to the target device are synchronously replicated to a second data storage system. On the first data storage system, each of the multiple cache pages may be synchronously replicated to the second data storage system. A lock on each of the cache pages is not released until an acknowledgement is received regarding successful replication of the cache page. On the second data storage system, requests to replicate the multiple cache pages containing write data of the multi-page write are received and processed using locks of corresponding cache pages on the second data storage system. Such techniques also handle concurrent reads and/or writes. Deadlock detection and resolution processing may be performed for concurrent writes.

Abstract: Described are data replication techniques. Y cycles of writes directed to a first storage device of a first data storage system are collected, Y>2. Each of the Y cycles denotes writes directed to the first storage device at an occurrence of a fixed time interval. Writes of cycle N?1 directed to the first storage device are transmitted from the first data storage system to a second data storage system. Writes of cycle N?2 are applied to a second storage device. An acknowledgement regarding cycle N?1 is sent from the second data storage system to the first data storage system responsive to determining that the writes of cycle N?1 directed to the first storage device have been received by the second data storage system and that the writes of cycle N?2 directed to the first storage device have been applied to the second storage device.

Abstract: Described are data replication techniques. Writes of cycle N directed to a first storage device of a first data storage system are received. Writes of cycle N?1 directed to the first storage device are transmitted to a second data storage system. Writes of cycle N?2 directed to the first storage device are applied to a second storage device of the second data storage system. An acknowledgement regarding cycle N?1 is sent to the first data storage system responsive to determining that the writes of cycle N?1 directed to the first storage device have been received by the second data storage system and that the writes of cycle N?2 have been applied to the second storage device. At least some writes of cycle N directed to the first storage device are transmitted to the second data storage system prior to the first data storage system receiving the acknowledgement regarding cycle N?1.

Abstract: Techniques are described for determining I/O workload. A first device of a first data storage system and a second device of a second data storage system are configured as synchronous mirrored devices of a first logical device. The host issues I/O operations to the first logical device over first and second paths. First I/O workload information is determined for a first data portion of the first logical device. Second I/O workload information is determined for the first data portion. The first I/O workload information and the second I/O workload information each include a first number of read operations that is a sum of read operations directed to the first logical device over both the first path and the second path. Data storage optimizations are performed on the first data storage system using the first I/O workload information and/or the second data storage system using the second I/O workload information.

Abstract: Ordering data writes includes at least some of a group of local storage devices receiving a first plurality of data writes, waiting for all of the local storage devices to be ready to switch cycles and causing a coordinated and synchronized cycle switch after all of the local storage devices are ready to switch cycles by sending a first command to each of the local storage devices where the first plurality of data writes are associated with a particular cycle on each local storage device in the group. Ordering data writes also includes at least some of the group of local storage devices receiving a second plurality of writes after initiating the coordinated and synchronized cycle switch where all of the second plurality of writes are associated with a cycle different from the particular cycle on each local storage device.

Abstract: A lighting apparatus with uniform illumination distribution, according to various embodiments, can include a lens for area lighting. In one embodiment, the lens comprises a plurality of cross-sections identified by a thickness ratio defined at different angles. The thickness ratio is determined relative to the thickness of the cross-section defined at a center angle of the lens. In another embodiment, the lighting apparatus with uniform illumination distribution includes a lens having an inner surface and an outer surface. A profile of the inner surface and the outer surface is composed of a plurality of piecewise circular arcs defined with radii and circle centers. The lens is formed as a complex curve lens by joining the piecewise circular arcs of the inner surface and the outer surface.

Abstract: A lighting apparatus with uniform illumination distribution, according to various embodiments, can include a lens for area lighting. In one embodiment, the lens comprises a plurality of cross-sections identified by a thickness ratio defined at different angles. The thickness ratio is determined relative to the thickness of the cross-section defined at a center angle of the lens. In another embodiment, the lighting apparatus with uniform illumination distribution includes a lens having an inner surface and an outer surface. A profile of the inner surface and the outer surface is composed of a plurality of piecewise circular arcs defined with radii and circle centers. The lens is formed as a complex curve lens by joining the piecewise circular arcs of the inner surface and the outer surface.