ESXi 5.5 supports iSCSI storage and up to 5 node MSCS cluster using Qlogic, Emulex and Broadcom adapters.
ESXi 5.5 supports iSCSI for Windows Server 2008 SP2, Windows 2008 R2 SP1 and Windows 2012 server. Windows Server 2003 is not supported.
Cluster-across-box (CAB) and cluster-in-a-box (CIB) are supported. A mixture of CAB and CIB is not supported.
No qualification is needed for SWiSCSI initiator in a guest operating system.
N+1 cluster configuration comprising of a cluster between "N" virtual machines on separate ESXi hosts and one physical machine running Windows natively is supported.
All hosts must be running ESXi 5.5.
Mixed cluster nodes running FC or FCOE and iSCSI are not supported.
Mixed mode of iSCSI config is supported. For example, Node A on ESXi with iSCSI software initiator and Node B on ESXi with Qlogic, Emulex or Broadcom hardware adapter.
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.