Abstract: Systems and methods are described for smoothing-out latency of IO operations processed by a distributed storage system. In some examples, latency is distributed among IO operations to more evenly spread processing of the IO operations over an IO processing interval. A target latency for IO operations for a volume of a distributed storage system is periodically calculated each sample period based on the number of IO operations to be processed during the next IO processing interval for the volume. As IO operations are received for the volume, a latency may be associated with the IO operation based on the target latency and the IO operation may be queued or synchronously processed as appropriate. Responsive to expiration of a time period that is based on at time at which a given IO operation at the head of the queue was received and the assigned latency, the given IO operation is dequeued and processed.

Abstract: Systems and methods are described for smoothing-out latency of IO operations processed by a distributed storage system. In some examples, latency is distributed among IO operations to more evenly spread processing of the IO operations over an IO processing interval. A target latency for IO operations for a volume of a distributed storage system is periodically calculated each sample period based on the target IOPS to be processed during the next IO processing interval for the volume. As IO operations are received for the volume, a latency may be associated with the IO operation based on the target latency and the IO operation may be queued or synchronously processed as appropriate. Responsive to expiration of a time period that is based on at time at which a given IO operation at the head of the queue was received and the assigned latency, the given IO operation is dequeued and processed.

Abstract: Methods and systems for managing Serial Advanced Technology Attachment (“SATA”) affiliation transfers between a requesting controller and a granting controller of a storage system. After receiving an affiliation request from the requesting controller, the granting controller queries a number of commands that are queued locally at the granting controller. The granting controller grants the affiliation to the requesting controller after a period of time that is determined based on the queried number of commands that are queue locally.

Abstract: Methods and apparatus for improved calculation of redundancy information in RAID storage controllers. Features and aspects hereof provide for a firmware/software element (FPE) for generating redundancy information in combination with a custom logic circuit (HPE) designed to generate redundancy information. A scheduler element operable on a processor of a storage controller along with the FPE determines which of the FPE and HPE is best suited to rapidly complete a new redundancy computation operation and activates or queues the new operation for performance by the selected component.

Abstract: Methods and apparatus for improved calculation of redundancy information in RAID storage controllers. Features and aspects hereof provide for a firmware/software element (FPE) for generating redundancy information in combination with a custom logic circuit (HPE) designed to generate redundancy information. A scheduler element operable on a processor of a storage controller along with the FPE determines which of the FPE and HPE is best suited to rapidly complete a new redundancy computation operation and activates or queues the new operation for performance by the selected component.

Abstract: Methods and systems for improved transfer of mirrored information between paired dual-active storage controllers in a storage system using a SCSI transport layer. A first portion (approximately half) of the mirrored information transfers are performed in accordance with a first manner in which the controller to receive the mirrored information issues a read operation on the initiator-target nexus (ITN) of the SCSI transport layer to retrieve the mirrored information. A second portion (approximately half) of the mirrored information transfers are performed according to a second manner in which the controller having the information to be mirrored sends the information to be mirrored to the partner controller using a write operation on the ITN. The read and write operations on the same ITN may thus overlap to improve inter-controller communications. The mirrored information may be cached write data or entire I/O requests to be shipped to a partner controller.

Abstract: Methods and apparatus for configurably limiting performance of an I/O controller device in processing of I/O requests. A performance monitor and control module in the I/O controller device monitors performance of the I/O request processing module and limits its processing to assure that maximum performance threshold values are not exceeded. In one embodiment, the performance monitoring may average performance over one or more periods of time and may provide a moving average window to determine the performance of the I/O controller device. The measured performance may determine a variety of performance measures each of which may be compared against one or more corresponding maximum performance threshold values. Requests that cannot be processed during a present period of time are delayed until a subsequent period of time to thereby limit performance of the I/O controller device.

Abstract: Methods and systems for managing Serial Advanced Technology Attachment (“SATA”) affiliation transfers between a requesting controller and a granting controller of a storage system. After receiving an affiliation request from the requesting controller, the granting controller queries a number of commands that are queued locally at the granting controller. The granting controller grants the affiliation to the requesting controller after a period of time that is determined based on the queried number of commands that are queue locally.