Some exceptions to the proposed configuration of the above article were done: I've used Microsoft SQL 2005 instead of SQL 2008 and I've not used the Microsoft iSCSI as shared storage: I've preferred to use Openfiler ESA version 2.99.2 that come with a good web interface to configure it and because I prefer Linux flavours :) .
After enabling software iSCSI on the two ESXi you will see the vmhba33 iSCSI Software adapter in your Configuration Storage Adapters vCenter Tab
Go to Configuration Networking and create a VMKernel Port on a standard vSwitch
I've found two articles on the web that help me configure the shared storage.
The first is "How to Configure LUN Masking with Openfiler 2.99 and ESXi 4.1" by Mike Brown: don't worry about the title... the configuration is the same also for vSphere 5.0
The second article - written in italian language - is "SAN iSCSI con Openfiler" by Alessio Carta.