I'm trying to debug something related to iSCSI LUN resizing.
In our setup we use Debian Linux 8 (jessie) with Open-iSCSI and multipath-tools connected to a FAS2552 (ONTAP 8.3.2RC2) device. When we resized our LUN from 6 TiB to 14 TiB yesterday some of the paths got in a weird state.
We noticed that the iSCSI clients (the Debian machines) detect the resize:
kernel: [5606835.845712] sd 1:0:0:0: Capacity data has changed
kernel: [5606842.329394] sd 2:0:0:1: Capacity data has changed
This is detected because the FAS2552 device is reporting this via iSCSI ("2A 09 CAPACITY DATA HAS CHANGED").
By tcpdumping we've been able to confirm that the FAS2552 device is sending the "2A 09 CAPACITY DATA HAS CHANGED" message (SCSI Response (Check Condition) LUN:0x00 - Additional Sense Code+Qualifier: Unknown (0x2a09)). It might be an issue in the Linux kernel, Debian 3.16.36-1+deb8u1 in this case. This could already have been solved in later versions of th Linux kernel. We'll report back to this forum post when we upgrade to Debian 9 (Stretch) and the issue is still there and bothering us.