A new feature was introduced in vSphere 5.5 called Permanent Device Loss (PDL) AutoRemoval. This KB outlines the feature, what it does and why. The basic idea behind it is to auto remove devices from an ESXi host when the device no longer returns SCSI sense codes. It helps to keep things clean and tidy.
When first hearing of this feature I thought there may be implications for vMSC environments (SVC stretched cluster running VMware) and this morning Duncan Epping from Yellow-Bricks confirmed this.
The recommendation is to disable PDL AutoRemoval for SVC Stretched clusters. If devices are auto removed it will cause undesirable behavior (the volumes will not be accessible from a VMware perspective without manual intervention) when access is restored.