ONTAP Discussions

LUN resize isn't always reported to iSCSI clients


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").

For some reason we got in this situation:


$ multipath -l
size=14T features='4 queue_if_no_path pg_init_retries 50 retain_attached_hw_handle' hwhandler='1 alua' wp=rw
|-+- policy='service-time 0' prio=0 status=active
| `- 3:0:0:0 sdc 8:32 active undef running
`-+- policy='service-time 0' prio=0 status=enabled
  `- #:#:#:# -   #:#  active undef running

I'm trying to reproduce this issue by creating a new 50G LUN and resizing the LUN, but the "Capacity data has changed" logline doesn't appear in our logs when we execute the resize.


In which case does a FAS2552 device report a resize of a LUN exactly? Or in other words, why doen't it report the resize on my 2nd LUN as it did on my 1st yesterday?



We've been debugging this issue a bit more.


  1. We found out that the multipath issue is related to https://bugs.debian.org/580972 which is solved in multipath-tools/0.5.0+git0.770e6d0d-3.
  2. 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.
NetApp on Discord Image

We're on Discord, are you?

Live Chat, Watch Parties, and More!

Explore Banner

Meet Explore, NetApp’s digital sales platform

Engage digitally throughout the sales process, from product discovery to configuration, and handle all your post-purchase needs.