VMware release KB 1008130 yesterday, describing just this:
- VMware ESX or ESXi host might get disconnected form VirtualCenter.
- All paths to the LUNs are in standby state.
- esxcfg-rescan might take a long time to complete or never completes (hung).
The KB goes on to say, that right now the only fix is a reboot:
This issue can occur on VMware ESX servers under the following conditions:
* Hypervisor version: VMware ESX 3.5 U3.
* SAN hardware: Active/Passive and Active/Active arrays (Fibre Channel and iSCSI).
* Trigger: This occurs when VMFS3 metadata updates are being done at the same time failover to an alternate path occurs for the LUN on which the VMFS3 volume resides .
A reboot is required to clear this condition.
VMware is working on a patch to address this issue. This knowledge base article will be updated after the patch is available.