ESXi 5.5 supports PSP_RR for MSCS.
Support for Windows Server 2008 SP2, Windows Server R2 SP1 and Windows 2012 server GOS only. Windows Server 2003 is not supported.
PSPs configured in mixed mode is supported. In a 2 node cluster one ESXi host can be configured to use PSP_FIXED and the other ESXi host can use PSP_RR.
Shared disk quorum or data must be provisioned to guest in PassThrough RDM mode only.
All hosts must be running ESXi 5.5.
Mixed mode configurations of ESXi 5.5 with previous ESXi releases are not supported.
Rolling upgrades of cluster Hosts from previous versions of ESXi to ESXi 5.5 builds are not supported.