Abstract: Methods and structure for load balancing of background tasks between storage controllers are provided. An exemplary active storage controller comprises a front-end interface that receives host Input/Output (I/O) requests directed to a logical volume, a back-end interface that couples with one or more of storage devices provisioning the logical volume, and a control unit. The control unit processes the host I/O requests directed to the logical volume, identifies a background processing task distinct from the host I/O requests and related to the logical volume, and assigns the background processing task to a passive storage controller for processing.

Abstract: Methods and structure for resuming background tasks in a storage environment. storage controller. The system is operable to receive host Input/Output (I/O) requests directed to a logical volume, and to couple with one or more of storage devices provisioning the logical volume. The system is further operable to process the host I/O requests directed to the logical volume, to initiate a background processing task distinct from the host I/O requests and related to the logical volume, and to store progress information on at least one of the one or more storage devices describing progress of the background processing task.

Abstract: Methods and systems for transferring ownership of a logical volume in a storage system comprising multiple storage controllers is provided. According to the method, the storage controllers are coupled for communication with a logical volume, wherein at least one storage device coupled with the storage controllers implements the logical volume. The method comprises identifying, at a first storage controller, a second storage controller to receive the logical volume. The method also comprises initiating a transfer of ownership of the logical volume from the first storage controller to the second storage controller by transferring metadata stored in a memory of the first storage controller to the second storage controller, the metadata existing in a native format that describes the configuration of the logical volume on the at least one storage device.

Abstract: Methods and structure for improved buffer management in a storage controller. A plurality of processes in the controller each transmits buffer management requests to buffer management control logic. A plurality of reserved portions and a remaining non-reserved portion are defined in a shared pool memory managed by the buffer management control logic. Each reserved portion is defined as a corresponding minimum amount of memory of the shared pool. Each reserved portion is associated with a private pool identifier. Each allocation request from a client process supplies a private pool identifier for the associated buffer to be allocated. The buffer is allocated from the reserved portion if there sufficient available space in the reserved portion identified by the supplied private pool identifier. Otherwise, the buffer is allocated if sufficient memory is available in the non-reserved portion. Otherwise the request is queued for later re-processing.

Abstract: Methods and system for implementing a clustered storage solution are provided. One embodiment is a storage controller that communicatively couples a host system with a storage device. The storage controller comprises an interface and a control unit. The interface is operable to communicate with the storage device. The control unit is operable to identify ownership information for a storage device, and to determine if the storage controller is authorized to access the storage device based on the ownership information. The storage controller is operable to indicate the existence of the storage device to the host system if the storage controller is authorized, and operable to hide the existence of the storage device from the host system if the storage controller is not authorized.

Abstract: Methods and structure for improved shipping of I/O requests among multiple storage controllers of a clustered storage system. Minimal processing of a received I/O request is performed in a first controller to determine whether the I/O request is directed to a logical volume that is owned by the first controller or to a logical volume owned by another controller. For requests to logical volumes owned by another controller, the original I/O request is modified to indicate the target device address of the other controller. The first controller then ships the request to the other controller and configures DMA capabilities of the first controller to exchange data associated with the shipped request between the other controller and memory of the host system.

Abstract: Methods and system are provided for exposing logical volumes to host systems and storage controllers in a consistent manner across a clustered storage system. One embodiment is a storage controller. The storage controller is operable to communicate with other storage controllers within the clustered storage system. The storage controller is further operable to generate a proposed Logical Unit Number (LUN) for a logical volume provisioned at the storage devices, and to communicate with each of the other storage controllers within the clustered storage system requesting that the other storage controllers determine if the proposed LUN is in use. If the proposed LUN is not in use, then storage controller assigns the proposed LUN to the logical volume. If the LUN is in use, then the storage controller generates a new proposed LUN and re-tries communication with the other storage controllers until a unique LUN is found.