Resolved without disabling IPv6 on Synology
I experienced this problem after upgrading my 3 node cluster from 7.4 to 8.2.4. I also have a Synology storage device connected via iSCSI and was experiencing symptoms exactly as described by others, with intermittent (mostly non-functional) graphs in the UI and iSCSI connection failure logs in the syslog.
I have iSCSI multipath configured, because I'm running a Synology UC3200 with dual controllers, so I need to have multiple paths to my storage working. See
here for more details about multipath. All was working fine before the upgrade.
I didn't want to disable IPv6 support as others have done, so here is how I solved it. The connection failures were occurring to IPv6 link local addresses. However, these addresses were not on any of my active Synology ports. I think what happened is that the Synology was connected via the 2nd LAN interface previously, but is now connected via the 1st LAN interface. At any rate, these IPv6 link local addresses were not reachable by my Proxmox nodes.
I performed the following on each of my Proxmox nodes, which restored graph operation without modifying my Synology config.
Steps to Resolve
Check the active sessions the node is using to communicate with the Synology storage.
Check the configured nodes on the system to which connections are being attempted.
Remove all nodes that don't have an active session.
Bash:
iscsiadm -m node -T <target> -p <ip:port> -o delete
Example (the square brackets around an IPv6 address are important):
Bash:
iscsiadm -m node -T iqn.2000-01.com.synology:proxmox-san.raid6.412a2ab768 -p [fe80::9209:d0ff:fe0a:7325]:3260 -o delete
If you need to remove all the entries for the same target, simply leave off the -p and all entries for that target will be removed.
Bash:
iscsiadm -m node -T <target> -o delete
Verify that all the undesirable entries have been removed.
You should now only see the targets that match the active sessions displayed earlier.
Restart the iscsid service.
Conclusion
These exact steps restored graph functionality for me without requiring any configuration changes on my Synology.