Hello,   On Dell PS Series SANs, you must be running EQL FW, 6.x or greater and the volume cannot be configured for EQL Replication.  That's both SYNC rep and ASYN rep.    Much depends on the version of Windows you are referring to.  Windows 2008 & R2 do NOT naively support UNMAP.   It's only supports the SSD TRIM command.  However, if you install the Dell HIT/ME software it installs a driver to change the TRIM command to an UNMAP command on the fly for Dell PS volumes.   This is only applicable to volumes that are DIRECTLY connected to the EQL volume via the MS iSCSI initiator in the host.  A VM on a VMFS partition isn't supported by HIT/ME software.    Windows 2K8 and R2 Hyper-V CSV volumes does not support UNMAP.  That's a MS issue, unrelated to the array.   Windows 2012 and R2 CSV volumes can support UNMAP only when using VHDX virtual disks, if using the old VHD reclaim isn't supported.   An additional benefit of HIT/ME in all supported cases, is via the Auto Snapshot Manger GUI you can force the reclaim option at any time.   Note: If you are using snapshots, you may not immediately get back the expected amount of space back.  The snapshot may still be referencing that data, so until the snapshots that reference it are removed it will remain allocated.   Regards, Don 
I know about the scsi unmap command for vmfs to reclaim space on an EQ LUN. Is there an equivalent for Windows data volumes connected via iscsi?
UNMAP for Windows volumes?