@acebmxer Thank you for your quick feedback.

@poddingue Thanks for looking into it further as well.. If there is a hard cap on the amount of NBD connections, then that is very interesting. Because the closest I've ever been able to find regarding this setting, was the general answer of "Try and see what works for you". So if ther is indeed a hard cap, then I would propose that this is limited inside the GUI itself. e.g. if the cap is 8, then don't let the integer exceed 8. I'm doing increasing increments of the number of connections now. So far I've done 1,2,10. And 10 does seem to be breaking again, but only on some. Thanks as well for the link. I'm collecting the logs through xen-bugtool --yestoall now. I do wish that something like this is implemented in GUI someday. And I even made a FR feedback on it. Since I really do want to provide good information for the devs. But collecting manually isn't the most convinient way unfortunately. Logs should be up shortly

Glad the start-delay removal got that VM going again. I checked and it's a real, documented XCP-ng parameter, "the delay to wait before a call to start up the VM returns", so that explains the behavior. I couldn't find auto_poweron_delay documented anywhere in the XCP-ng or XO docs, so I'm not sure if it's something XO's advanced VM settings expose under a different name, or something unrelated you picked up while googling. If you check the VM's Advanced tab in XO and see what's actually set there, that would help pin down which setting you're really dealing with. Either way this looks like a gap in the autostart guide, since it doesn't mention that start-delay can interact with autostart at all.

Yes, you can force start and remove the backup job and that's it.

Hello, You can find all the demo dashboards at the following address: https://github.com/steeve-san/OpenMetrics_XCP_Grafana Regard,

This issue should be fixed in the latest release (to be out today).

Hello @anthoineb, We captured another occurrence on the same VM, os-ott-data-3-2 (172.30.52.193), on the same hypervisor and QCOW2 VDI as the incident reported on 2026-07-25. This occurrence is useful because xen_blkfront.max_ring_page_order=3 was definitely active: xenstore showed ring-page-order=3 with eight ring references; the guest queue depth was 256; 255 write requests remained in flight; all 256 blk-mq scheduler tags were busy; wbt_lat_usec=0; I/O PSI full was approximately 98%; completed xvdb counters did not advance between samples. The backend state was nevertheless the same as in the previous capture: tapdisk was sleeping in scheduler_wait_for_events(); tap-ctl reported reqs_outstanding=0; tap request counters were 0/0; req_prod=0 and rsp_prod=0; no tap, image, VBD, map or xenbus errors were reported. One detail may be relevant: GDB still printed n_reqs=32 and n_reqs_free=32, although the frontend had negotiated an order-3 ring and the guest exposed 256 tags. Is this expected because n_reqs represents a separate fixed tapdisk request pool, or could it indicate that tapdisk is not observing the complete multi-page ring? The controller captured GDB and the guest/hypervisor state before reboot. After the ten-minute diagnostic window, the same signature was confirmed three more times and the VM was rebooted. It rejoined the cluster successfully. I have attached: the complete GDB/tap-ctl capture; the guest blk-mq, diskstats, PSI, D-state stack and kernel-journal snapshot; the corresponding tapdisk/xenstore, daemon.log and SMlog excerpt; a README and SHA-256 checksums. The important new result appears to be that increasing max_ring_page_order from 0 to 3 did not prevent the stall; the same mismatch recurred with 255/256 frontend requests/tags occupied while the backend ring and tapdisk remained empty. 20260730-005220-gdb-172.30.52.193.txt 20260730-pre-reboot-guest-172.30.52.193.txt 20260730-pre-reboot-hypervisor-172.30.50.191.txt README.txt SHA256SUMS.txt