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: 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 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: In one embodiment, a method is provided comprising: receiving, at a virtualizer, a write command from an initiator in a storage area network, wherein the storage area network includes the initiator and a plurality of mirrored storages; sending, from the virtualizer, a write command to the plurality of mirrored storages; receiving, at the virtualizer, a transfer ready message from a first of the plurality of mirrored storages; sending a transfer ready message from the virtualizer to the initiator in response to the receiving of the transfer ready message from the first of the plurality of mirrored storages; receiving, at the virtualizer, a data message from the initiator; and sending, from the virtualizer, a data message to the plurality of mirrored storage once transfer ready messages have been received from each of the plurality of mirrored storages.

Abstract: Methods and apparatus are provided for alleviating deadlock and controlling congestion in a network such as a fibre channel network. Techniques are provided for detecting stalled frames at a fibre channel switch. Reserve credits are released when stalled frames are detected. In some instances, reserve credits are released after a predetermined period of time. Reserve credits allow transmission to effectively reduce deadlock and congestion. Reserve credits are particularly effective in reducing deadlock resulting from transient loops in a fibre channel network.

Abstract: A fibre channel frame is received at a first fibre channel switch. The fibre channel frame includes time stamp information associated with fibre channel switches between a second fibre channel switch and the first fibre channel switch. A time-to-live (TTL) value included in the fibre channel frame is determined. The fibre channel frame is sent back to the second fibre channel switch upon determining the TTL value included in the fibre channel frame.

Abstract: Methods and apparatus are provided for determining characteristics associated with routes in fibre channel networks. Techniques are provided for inserting time stamp information into frames transmitted from a source to a destination and back to the source. Time stamp information allows a supervisor associated with a source to determine characteristics such as round trip times, latency between hops, and connectivity to a destination for specific routes.

Abstract: Methods and apparatus are provided for determining characteristics associated with routes in fibre channel networks. Techniques are provided for inserting time stamp information into frames transmitted from a source to a destination and back to the source. Time stamp information allows a supervisor associated with a source to determine characteristics such as round trip times, latency between hops, and connectivity to a destination for specific routes.

Abstract: Methods and apparatus are provided for controlling congestion in a network such as a fibre channel network. Techniques are provided for characterizing traffic flow at a congested network node. The congested network node can generate various instructions such as quench messages to control traffic flow towards the congested network node. The quench messages can optionally include information about the characteristics of the congestion. The instructions are distributed to other nodes in the network. The other network nodes can interpret the instructions and control traffic flow towards the congested node.