Hey Jazsko, why not VSan?
Also we've been looking at a new solution as well to replacing our aging HP Lefthands. We have almost exactly the same environment you havel. Three ESXi 5.1 hosts on 3 Dell r420 Poweredge servers with an iSCSI connection to our SAN environment sitting on a dedicated Gigabit backbone where each ESX host has an aggregated LAG group of 4 GB Nic ports each. The big reason we're moving is due to the age of the LeftHands and the limitation of IOPS (capping at 2400 on a regular basis) I've spent the past month courting NetApp, Vsan, EMC, Compellent, Equal logic, Nimble, a hosted solution, data center hosting for storage, and a hosted leasing by the TB solution from another vendor. So far they are listing from best to least: 1. Nimble CS220, 2. NetApp FS2552, 3. Vsan, 4. EMC VNXe3200, and the rest are off the board because of the prohibitive cost of IOPs/$ based off the number of spindles needed to get to the IOPs i'm looking for. Complete FLASH arrays are completely off the board due to cost and failure rates of a complete read/write SSD environment over time. Both Nimble and NetApp do preprocessing at the ram cache level, but Nimble has the speed there due to sequential writes and compression methodologies i've seen so far. EMC VNXe3200 shows signs of similar technology, but I have yet to do a deep dive on the tech with the engineer to get to the guts of the data processing path. VSan may move off the list just due to how new the tech is, but if you're just looking for compute and capacity in your storage solution and not all the fancy software that comes with most of the other solutions, you'll find that the price is much more cost effective, but its a home grown system you'll be running even if you do have support from VMware as long as the hardware you use is on their HCL.
Ted B.