vmware standalone 5.1 complains about block size for Equallogic ISCSI storage

this is not related to eql. eql can create luns up to 15tb at this time. your question focuses on vmware. the answer is: no. vsphere 5.1 still has the 2tb vmdk limit. only via extends or physical mode rdms possible at this time.

Like joergriether mentioned, (physical) RDM is one option, but you can also do guest attached iSCSI. A third option is to use Windows dynamic disk on top of 3 x 2TB VMDK disks, but I would highly recommend against that as dynamic disk spanning is just a bad practice in general (only use it if you have to have a raid (1 or 5) option and really cannot budget a decent raid controller.

If opting for guest attached iSCSI, be sure not to use the same vmnics for host iSCSI as you are using for guest iSCSI. In other words; 2 vSwitches with a single vmnic each on 2 different subnets for the physical server (host) iSCSI connectivity (for the boot drive of the VM and maybe also for other VMs), then install MDSM on that VM, create 2 more vSwitches with a single vmnic in each, and create a vm portgroup in each. Then you give the VM 2 extra NICs (on top of the regular NICs you plan to give it); each to 1 of the vmpg's and use properly MD multipathing to connect the VM to its own 6TB virtual disk on the SAN. VMware will only be providing the path to the SAN for this 6TB disk at this point, but will not know about the existence of this disk. This also means that VMware based snapshots will not include the data on this (virtual) disk (however physical raw device mapping also excludes the disk from VMware snapshots).