@TestForEcho No ETA for now. Even before supporting QCOW2 on LINSTOR, we have several points to robustify (HA performance, potential race conditions, etc.). Regarding other important points:
Supporting volumes larger than 2TB has significant impacts on synchronization, RAM usage, coalesce, etc. We need to find a way to cope with these changes.
The coalesce algorithm should be changed to no longer depend on the write speed to the SR in order to prevent potential coalesce interruptions; this is even more crucial for LINSTOR.
The coalesce behavior is not exactly the same for QCOW2, and we believe that currently this could negatively impact the API impl in the case of LINSTOR.
In short: QCOW2 has led to changes that require a long-term investment in several topics before even considering supporting this format on XOSTOR.