Hello,   There's not much info here to go on. I would start with making sure that the server is configured per Dell's best practice doc.  en.community.dell.com/.../20434601.aspx The VMware iSCSI configuration won't affect Guest iSCSI connection speed.   Ideally, Guest iSCSI traffic should have it's own NICs separate from the NIC ESXi is using for it's iSCSI traffic.  Make sure that VMware tools is installed as well.  That will make sure the network driver is optimized.  Running the current version of ESXi is important too.  There have been some KBs about performance issues with the VMXNET3 adapter.   Sometimes changing to the E1000 might actually work better. 
SAN is a PS4100 with dedicated switches. In VMware I have a vSwitch setup according to the DELL EQ Documentation. The VMKernal Properties are as follow: NIC Teaming Tab Settings: One Adapter is set to Active the other in placed into Unused. This order is switched for the second VMKernal iSCSI connection. The DELL MPIO extension was added to the VMware host and the connection is set to use DELL_PSP_EQL_ROUTED for Managed Paths to the ISCSI target. Managed Paths also show Active / Active status. Testing throughput with a physical server through a single iSCSI Initiator to dedicated Lun show speeds fully saturating the link with 99MB/s throughput. All I can manage from inside the Server 2012 guest OS, with vmxnet3 network adapter, which is also on the SAN is around the 30MB throughput. The speed drops even more when transferring from a Fiber Channel AX150 SAN hosted VMware guest OS, with an Intel Pro 1000 MT network adapter, to a PS4100 SAN share, it drops to 13MB/s. What did I miss, and where should I look to make changes?  What should I look at for increasing the throughput?
iSCSI speed in VMware guest - slow