iSCSI issues after upgrading to 11.2 x64 RELEASE

Tue Sep 4 17:08:57 UTC 2018

04.09.2018 23:57, Ryan Moeller wrote:

>> The NIC's are Intel based using igb kernel driver:
>>
>> igb0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000
>> options=6403bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
> 
> I see your MTU is 9000, and as described by the other thread you linked to, there are issues with 9k jumbo cluster allocation.
> Some detailed notes are here, but the quick summary is: set MTU < 4096
> https://gist.github.com/freqlabs/eba9b755f17a223260246becfbb150a1
> 
>> Can anyone suggest anything to stop my system from completely locking up and becoming unresponsive?
>> At the moment I'm not sure if switching to 'Stable' or 'Current' branches is a good solution?
> 
> The problem has been mitigated for a while on 12-CURRENT, so that might be worth trying. Otherwise I’ve been hoping a committer will put this fix in 11-STABLE, but in the meantime you could manually apply the patch:
> https://reviews.freebsd.org/D16534 <https://reviews.freebsd.org/D16534>

Intel NIC users also should be aware of chip hardware problems while dealing with 9k MTU, like documented here:
https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/i218-i219-ethernet-connection-spec-update.pdf

In short, Intel does not recommend MTU over 8500.