Expand Using Xen Center 5.x

1. Identify the iSCSI SR to adjust. Document all settings.
2. Shut down all guests using this iSCSI SR.
3. Make sure you have all iSCSI settings documented.
4. Right click on the iSCSI SR, select Detach.
5. Right click on the iSCSI SR, select Reattach.
6. Depending on your configuration, you may need to reenter some settings.

Źródło: http://jacobackerman.blogspot.com/2009/06/expanding-xenserver-iscsi-storage.html