Abstract: Technologies for providing recovery point review within a continuous data protection system can support a data storage operator in a data recovery procedure. A snapshot image can be chosen that was made prior to a data loss event. A new writable snapshot can be created from this logged snapshot. The new writeable snapshot can become the target for recovering the data volume. Review can be performed in a forward direction by reading a journal of I/O operations that have occurred since the prior snapshot was made. Review can be performed in a backward direction by deriving a dirty data list of changes made to the data volume and then removing the changes as requested. The operator can continue forward and backward review operations to refine the selected recovery point. Upon establishing the desired recovery point, the new writable snapshot can be committed, or rolled back, onto the data storage volume.

Abstract: Technologies are described herein for performing a multi-protocol data transfer. A first protocol that guarantees reliability and in-order delivery of data packets is utilized to transmit control information for a data transfer. Once the control information has been transmitted and received at the destination, a second protocol is utilized to transfer the actual data. The second protocol does not guarantee data reliability or in-order delivery. If any data packets are not delivered to the destination using the second protocol, either the first protocol, the second protocol, or a combination can be utilized to retransmit the missing packets.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Technologies are described for implementing a default migration mechanism in a storage system containing multiple tiers of storage with each tier having different cost and performance parameters. Data that is accessed more frequently can be migrated toward higher performance storage tiers while data that is accessed less frequently can be migrated towards lower performance storage tiers. Default migration behavior can be overridden by user-specified values for tier age residency policy, demotion policy, tier occupancy of volumes, and tier assignment. Data migration can be paused by the user and resumed by the user.

Abstract: Systems and methods for maintaining data consistency across mirrored storage nodes. Data consistency may be maintained in networked storage environments using a timestamp of an I/O in the primary and secondary servers (also referred to as nodes) in synchronous replication to re-synchronize the data efficiently, without much performance drop and while reducing the memory footprint. According to an aspect presented herein, data consistency is maintained in a mirror node by timestamping the I/O for a volume's logical territory in both the primary and secondary nodes. The timestamp acts as a watermark. Thus, whenever a disaster or failure occurs, the watermark point determines the re-synchronization point.

Abstract: Technologies are described herein for performing a multi-protocol data transfer. A first protocol that guarantees reliability and in-order delivery of data packets is utilized to transmit control information for a data transfer. Once the control information has been transmitted and received at the destination, a second protocol is utilized to transfer the actual data. The second protocol does not guarantee data reliability or in-order delivery. If any data packets are not delivered to the destination using the second protocol, either the first protocol, the second protocol, or a combination can be utilized to retransmit the missing packets.

Abstract: Technologies are described herein for providing bi-directional communication between redundant storage controllers in a storage system. One of the storage controllers operates in the initiator role over a point-to-point communication channel connecting the controllers, while the other operates in the target role. To transmit a function call from a storage module executing on the initiator storage controller to a corresponding module executing on the target storage controller, the initiator storage controller issues a write command to the second storage controller over the point-to-point communication channel. In order to transmit a function call from a storage module executing on the target storage controller to a corresponding module executing on the initiator storage controller, the target storage controller responds to a pending anticipatory read command sent from the initiator storage controller over the point-to-point communication channel.

Abstract: Technologies are described herein for skipping snapshots during a snapshot replication process in order to maintain an established recovery point objective. A first snapshot is selected after a previously replicated snapshot. A creation time of the first snapshot is retrieved. A difference between a current time and the creation time of the first snapshot is computed. A determination is made as to whether the difference is less than a recovery point objective. If the difference is less than a recovery point objective, then the first snapshot is replicated in the snapshot replicated process. If the difference is not less than a recovery point objective, then the first snapshot is skipped through the snapshot replication process.

Abstract: Technologies are described herein for providing assisted asynchronous replication between a first storage server having a first current state and a second storage server having a second current state. An instruction to roll back a first storage server from the first current state to a previous state according to a previous snapshot is received. The first storage server is then rolled back from the first current state to the previous state according to the previous snapshot. A determination is made as to whether the previous snapshot is available on a second storage server. Assistance data is then retrieved. A last consistency point common to the first storage server and the second storage server based on the assistance data is identified, where the last consistency point is at or prior to the previous snapshot. The second storage server is rolled back from the second current state to the last consistency point.

Abstract: Technologies are described for implementing container space management (CSM) in a data storage system. Performance may be improved by ensuring that the maximum number of drive spindles is made available to I/O loads. This may be accomplished by distributing data equally amongst all drive spindles, even if the drive spindles are in different logical drives. A workflow analysis may be performed to determine when the I/O load on the storage system is low and thus identify preferred times for background data re-striping. Data may be re-striped in a minimum number of movements using a data placement algorithm and data placement maps to select data to be re-striped. The data may be re-striped such that the most frequently accessed data within a tier is moved first. Such re-striping can be performed in a manner which optimizes the performance of the storage system both during, and after, the re-striping process.

Abstract: Technologies are described herein for high-performance and space efficient journaling mechanisms. A journal queue can buffer incoming I/O operations. The queue can be read by a journal write module. The journal write module can form metadata headers to store into the journal along with each I/O operation. Compound metadata headers may be formed for multiple I/O operations and the combination of multiple I/O operations may be efficiently stored to the journal as one journal write. Multiple journal entries may be written into the journal in parallel while maintaining the sequential ordering of the journal. A queue depth threshold can be established for determining if journal entries should be combined into compound entries or not. Multiple concurrent readers can support continuous data protection, and various data replication features. Each reader can be represented as a reader pointer and a journal writer can invalidate reader pointers when related data is overwritten.