Enterprise data centers that utilize virtualization technologies often include multiple servers (also referred to herein as “hosts”) that share access to storage devices (e.g., disk arrays, etc.) through a storage area network (SAN). Each host is able to support simultaneous execution of multiple virtual machines (VMs). By storing VM images (also referred to as virtual disk files) in a SAN that is commonly accessible by multiple servers, a data center is able to launch any particular virtual machine on any of the servers thereby providing the data center an increased capability to manage its computing resources efficiently. For example, using technologies such as VMware's VMotion™ technology, a data center can perform a “live migration” of a VM that is running on one host to another host in the event that the first server is failing or underperforming. The new host is able to support the migration of the VM because, in part, it is able to access the VM's image that is stored on shared storage accessible by both the new host and the original host.
When a VM is launched on a host, the VM negotiates a connection session with the SAN in order to gain access to the VM's image which resides in a particular logical unit number (LUN) or data volume of the SAN. For example, if the host is physically connected to a Fiber Channel (FC) switch of the SAN, the VM (or host, on behalf of the VM) may request that the FC switch allocate to the VM a unique identifier referred to as a “virtual port” (Vport) that is associated with the actual physical port of the FC switch that connects to the host and that has been granted access to the LUN containing the VM's virtual disk file. In this manner, any request for data transmitted by the VM (or the host on behalf of the VM) that includes the allocated Vport and is received at the particular physical port of the FC switch can be identified by the FC switch as a request from the specific VM. As should be recognized, the use of such Vports provides FC switches the ability to simultaneously support different VMs (i.e., residing on the same host) at a single physical port by distinguishing among data requests from the different VMs that reside on the same host (i.e., connected to the FC switch via the same physical port) and thus handle such data requests appropriately, for example, by routing them to the correct LUNs, etc.
Because FC switches bind Vports to particular physical ports on the FC switch, Vports cannot be maintained during live migration of a VM from one host to another host. In particular, because the new host supporting the VM after live migration is necessarily connected to the FC switch (or a different FC switch) on a different port, the FC switch will generate errors or faults if it receives data requests from the VM that include the same Vport as used by the VM when it was running on the original host (and which was bound to a different physical port). Instead, during a live migration, the VM requests deletion of its original Vport on the original host, thereby tearing down its current connection session with the FC switch, and upon the VM's instantiation on the new host, negotiates a new connection session with the FC switch with a new Vport. In certain environments or implementations, multiple Vports may need to be created and deleted at the FC switch in order complete a live migration, thereby consuming a significant amount of time in the live migration process. For example, prior to migrating a VM to a new host, during a “pre-flight check” stage, the new host may need to first negotiate a Vport connection session with the FC switch to which it is connected to initially confirm that the new host is able to connect to the particular LUN in the SAN that stores the VM's virtual disk file. If the new host is indeed able to connect to the particular LUN storing the VM's virtual disk file, then it is an appropriate candidate to host the VM and will tear down the Vport connection session. When the new host receives the VM through live migration, it will again create a new Vport connection session in the FC switch to support the running VM.