Ran into a problem with a synology DS1815+ and though this could be helpful for others.

On the latest auto update to 6.0.1-3793 the iSCSI target(s) can become corrupt on the DS thus breaking the iscsi connection to the DS.

You can change the chap authentication info on the DS’s target and the globalsan iscsi initiator client, all you will see in the /var/log/iscsi.log is the following in regards to authentication.

[code]
Jun 6 00:23:20 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
Jun 6 00:23:25 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
Jun 6 00:23:33 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
Jun 6 00:23:45 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
Jun 6 00:23:55 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
Jun 6 00:24:08 syndisk kernel: [ 108.880447] iSCSI: iSCSI Login negotiation failed.
[/code]

But you just changed passwords on the DS target and client connecting, how could this be? The config file is either corrupt or has become unstable and the act of deleting the target (saving the lun) and recreating the target , pointing at that old lun suddenly gets you back in business.

Steps to fix:

Delete current target on the DS (save the lun)

Create a new target (set password)and attach to the lun you just saved, verify pass on globalsan client.

And that’s it.