Abstract: Methods and apparatus for managing exchanges in a network device of a storage area network are disclosed. In a first “host-side” exchange initiated by an initiator and between the initiator and the network device, one or more frames are received from an initiator and/or sent to the initiator. At least one of the frames pertains to access of a virtual storage location of a virtual storage unit representing one or more physical storage locations on one or more physical storage units of the storage area network. One or more “disk-side” exchanges between the network device and one or more targets (i.e., physical storage units) are initiated in response to the first exchange. In the disk-side exchanges, one or more frames are sent from the network device to one of the targets and/or received from the target. Exchange information for the host-side exchange and the associated disk-side exchanges are updated throughout the exchanges.

Abstract: Methods and apparatus for managing exchanges in a network device of a storage area network are disclosed. In a first “host-side” exchange initiated by an initiator and between the initiator and the network device, one or more frames are received from an initiator and/or sent to the initiator. At least one of the frames pertains to access of a virtual storage location of a virtual storage unit representing one or more physical storage locations on one or more physical storage units of the storage area network. One or more “disk-side” exchanges between the network device and one or more targets (i.e., physical storage units) are initiated in response to the first exchange. In the disk-side exchanges, one or more frames are sent from the network device to one of the targets and/or received from the target. Exchange information for the host-side exchange and the associated disk-side exchanges are updated throughout the exchanges.

Abstract: Methods and apparatus for managing exchanges in a network device of a storage area network are disclosed. In a first “host-side” exchange initiated by an initiator and between the initiator and the network device, one or more frames are received from an initiator and/or sent to the initiator. At least one of the frames pertains to access of a virtual storage location of a virtual storage unit representing one or more physical storage locations on one or more physical storage units of the storage area network. One or more “disk-side” exchanges between the network device and one or more targets (i.e., physical storage units) are initiated in response to the first exchange. In the disk-side exchanges, one or more frames are sent from the network device to one of the targets and/or received from the target. Exchange information for the host-side exchange and the associated disk-side exchanges are updated throughout the exchanges.

Abstract: Fine granularity exchange level load balancing may be performed in a device in a storage area network in order to ensure that processors in a multi-core environment are not overloaded. This may be accomplished by assigning input/outputs relating to a particular exchange to a specific processor, and maintaining that association so that subsequent related input/outputs are handled by the same processor. In this process, the system may first determine if a received IO is new. If so, then it may assign the IO to a particular data path processor and create a context corresponding to the IO and the processor, as well as to the type of the non-command frame. Subsequently, an event may be received corresponding to the IO, which may then be forwarded to the processor assigned to the IO.

Abstract: A metric measurement mechanism is used to determine network characteristics such as latency and round trip time with more precision than that available from layer three metric measurement mechanisms. The metric measurement mechanism can use the same architecture used by layer three metric measurement mechanisms while more accurately measuring network latency and isolating network device processing delays.

Abstract: In one embodiment, a solution is provided wherein a minimum and/or maximum bandwidth may be guaranteed for specific flows. These guarantees can be associated to various levels of granularity, such as target (T), target-Logical Unit Number (LUN) coupling (TL), initiator-target-LUN coupling (ITL), and initiator-target coupling (IT). This may be accomplished by rate limiting frames in the storage area network based upon quality of service information provided by a user. As such, the traffic can be shaped in a way that guarantees requested levels of service without dropping frames.

Abstract: In one embodiment, a solution is provided wherein a lock client sends lock requests to a lock manager upon receipt of an input/output (I/O) and receives back a lock grant. At some point later, the lock client may send a lock release. The lock manager, upon receipt of a lock release from a lock client, remove a first lock request corresponding to the lock release from a lock grant queue corresponding to the lock manager. Then, for each dependency queue lock request in a dependency queue corresponding to the first lock request, the lock manager may determine whether the dependency queue lock request conflicts with a second lock request in the lock grant queue, and then may process the dependency queue lock request according to whether the dependency queue lock requires conflicts with a second lock request in the lock grant queue.

Abstract: A method and apparatus to improve the performance of a SCSI write over a high latency network. The apparatus includes a first Switch close to the initiator in a first SAN and a second Switch close to the target in a second SAN. In various embodiments, the two Switches are border switches connecting their respective SANs to a relatively high latency network between the two SANs. In addition, the initiator can be either directly connected or indirectly connected to the first Switch in the first SAN. The target can also be either directly or indirectly connected to the second Switch in the second SAN. During operation, the method includes the first Switch sending Transfer Ready (Xfr_rdy) frame(s) based on buffer availability to the initiating Host in response to a SCSI Write command from the Host directed to the target. The first and second Switches then coordinate with one another by sending Transfer Ready commands to each other independent of the target's knowledge.

Abstract: Support for virtualization in a storage area networks may be provided using a variety of techniques. In one embodiment of the present invention, exchange level load balancing may be provided by determining if input/outputs (IOs) received by a device are new. If a particular IO is new, the IO may be assigned to a particular data path processor and an context may be created corresponding to the IO and to the processor. Then, when an event corresponding to the IO is received, the event may be forwarded to the processor assigned to the IO.

Abstract: In one embodiment, a solution is provided wherein a lock client sends lock requests to a lock manager upon receipt of an input/output (I/O) and receives back a lock grant. At some point later, the lock client may send a lock release. The lock manager, upon receipt of a lock release from a lock client, remove a first lock request corresponding to the lock release from a lock grant queue corresponding to the lock manager. Then, for each dependency queue lock request in a dependency queue corresponding to the first lock request, the lock manager may determine whether the dependency queue lock request conflicts with a second lock request in the lock grant queue, and then may process the dependency queue lock request according to whether the dependency queue lock requires conflicts with a second lock request in the lock grant queue.

Abstract: In one embodiment, a solution is provided wherein a lock manager is kept moving among multiple cores or processors in a multi-core or multi-processor environment. By “hopping” the lock manager from processor to processor, a bottleneck at any of the processors is prevented. The frequency of movement may be based on, for example, a counter that counts the number of input/outputs handled by the lock manager and moves the lock manager to a different processor once a determined threshold is met. In another embodiment of the present invention, the frequency of the movement between processors may be based on a time that counts the amount of time the lock manager has been operating on the processor and moves the lock manager to a different processor once a predetermined time is reached.

Abstract: In one embodiment, a solution is provided wherein a lock client sends lock requests to a lock manager upon receipt of an input/output (I/O) and receives back a lock grant. At some point later, the lock client may send a lock release. The lock manager, upon receipt of a lock release from a lock client, remove a first lock request corresponding to the lock release from a lock grant queue corresponding to the lock manager. Then, for each dependency queue lock request in a dependency queue corresponding to the first lock request, the lock manager may determine whether the dependency queue lock request conflicts with a second lock request in the lock grant queue, and then may process the dependency queue lock request according to whether the dependency queue lock requires conflicts with a second lock request in the lock grant queue.

Abstract: Methods and apparatus are provided for efficiently selecting virtualization engines in storage area networks. Initiators, targets, and candidate virtualization engines associated with a virtual logical unit number (VLUN) are identified and characteristics such as latency, network topology, load, and mirroring and striping characteristics are analyzed and used to efficiently select a virtualization engine for a particular VLUN in a storage area network. A virtualization engine can be implemented in a line card associated with a fibre channel switch.

Abstract: In one embodiment, a solution is provided wherein a minimum and/or maximum bandwidth may be guaranteed for specific flows. These guarantees can be associated to various levels of granularity, such as target (T), target-Logical Unit Number (LUN) coupling (TL), initiator-target-LUN coupling (ITL), and initiator-target coupling (IT). This may be accomplished by rate limiting frames in the storage area network based upon quality of service information provided by a user. As such, the traffic can be shaped in a way that guarantees requested levels of service without dropping frames.

Abstract: Support for virtualization in a storage area networks may be provided using a variety of techniques. In one embodiment of the present invention, exchange level load balancing may be provided by determining if input/outputs (IOs) received by a device are new. If a particular IO is new, the IO may be assigned to a particular data path processor and an context may be created corresponding to the IO and to the processor. Then, when an event corresponding to the IO is received, the event may be forwarded to the processor assigned to the IO.

Abstract: In one embodiment, a solution is provided wherein a lock manager is kept moving among multiple cores or processors in a multi-core or multi-processor environment. By “hopping” the lock manager from processor to processor, a bottleneck at any of the processors is prevented. The frequency of movement may be based on, for example, a counter that counts the number of input/outputs handled by the lock manager and moves the lock manager to a different processor once a determined threshold is met. In another embodiment of the present invention, the frequency of the movement between processors may be based on a time that counts the amount of time the lock manager has been operating on the processor and moves the lock manager to a different processor once a predetermined time is reached.

Abstract: Fine granularity exchange level load balancing may be performed in a device in a storage area network in order to ensure that processors in a multi-core environment are not overloaded. This may be accomplished by assigning input/outputs relating to a particular exchange to a specific processor, and maintaining that association so that subsequent related input/outputs are handled by the same processor. In this process, the system may first determine if a received IO is new. If so, then it may assign the IO to a particular data path processor and create a context corresponding to the IO and the processor, as well as to the type of the non-command frame. Subsequently, an event may be received corresponding to the IO, which may then be forwarded to the processor assigned to the IO.

Abstract: In one embodiment, a solution is provided wherein a lock client sends lock requests to a lock manager upon receipt of an input/output (I/O) and receives back a lock grant. At some point later, the lock client may send a lock release. The lock manager, upon receipt of a lock release from a lock client, remove a first lock request corresponding to the lock release from a lock grant queue corresponding to the lock manager. Then, for each dependency queue lock request in a dependency queue corresponding to the first lock request, the lock manager may determine whether the dependency queue lock request conflicts with a second lock request in the lock grant queue, and then may process the dependency queue lock request according to whether the dependency queue lock requires conflicts with a second lock request in the lock grant queue.

Abstract: A metric measurement mechanism is used to determine network characteristics such as latency and round trip time with more precision than that available from layer three metric measurement mechanisms. The metric measurement mechanism can use the same architecture used by layer three metric measurement mechanisms while more accurately measuring network latency and isolating network device processing delays.

Abstract: Methods and apparatus are provided improving data access efficiency in a storage area network. Mechanisms are provided to allow a virtual disk address to be efficiently mapped to a particular physical partition in a virtual disk while recognizing the mirroring, striping, and concatenation characteristics associated with the virtual disk. A variety of indices are used to allow direct access of a physical partition upon identification of a virtual disk address.