In Microsoft Windows 2012 and above there is cool role is introduced by Microsoft. Name of the role is iSCSI Target Server under File and Storage services. (Although there is same software provided by Microsoft earlier now they have given the same as role inbuilt in Server 2012, Earlier version iSCSI Target configuration), I used it to configure my Microsoft Clustering LAB, as it required shared storage. You can use Microsoft windows 2012 iSCSI Target is better substitute to freeNas or Openfiler.
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vGeek: Configuring Microsoft iSCSI Target datastore on Esxi server and multipathing Step by Step