Disclaimer: I work for LINBIT, makers of DRBD and LINSTOR the tech behind XOSTOR.
We can do highly available iscsi targets, we even have guides on our website that take you step by step to do it. These would be outside of XCP-NG, but would serve the same purpose.
If there is any interest from Vates to integrate DRBD/HA into XCP-NG, we're always open to discussions.
