Problem installing Windows to a iSCSI drive via iPXE

[psfan]

I setup a DHCP/TFTP and iscsi target server box (win2012r2) to boot client, pxe boot chained to undionly.kpxe.
When client booted up, I saw ipxe showed "Preserving SAN device 0x80"
Since the iscsi drive had no OS installed, it turned to boot from the 2nd boot device - an installation DVD for windows 2008 r2 standard server.
After entering the setup interface to select destination disk, the iscsi drive was in "offline" status, putting the iscsi drive online and I cannot go the next step, receiving error message:
"Windows cannot be installed to this disk. This computer’s hardware may not support booting to this disk. Ensure that the disk’s controller is enabled in the computer’s BIOS menu."
Whatever I treated the iscsi drive, creating partition, formatting, converting to mbr..., all not work.
And I noticed one thing that during the installation prebooting, the iscsi target was found to turn to "disconected" before entering "select language" stage. So I doubt that something caused the installation program disconnected from iscsi drive that make the setup failed.

Any help will be greatly grateful!