IBM TotalStorage DS300 Best Practices Manual page 447

Failover in case of a controller failover in the DS300
In this test, the network cable from eth3 of controller A of the DS300 is
unplugged. This leads to a controller failover in the DS300. IO is again created
during the test with the following command:
dd if=/dev/urandom of=/mnt/danube-disk1/10GBfile bs=1M count=10000
Example 7-17 shows some logging information as the controller failover starts.
Example 7-17 /var/log/messages as controller failover starts
Aug 3 13:39:56 danube kernel: iSCSI: target requests logout within 5 seconds
for session to danube-disk1
Aug 3 13:39:56 danube iscsid[7009]: socket 1 closed by target
Aug 3 13:39:56 danube iscsid[7009]: discovery session to 192.168.1.61:3260
failed to recv a PDU response, reconnecting
Aug 3 13:39:56 danube iscsid[7009]: cannot make connection to
192.168.1.61:3260: Connection refused
Aug 3 13:39:56 danube iscsid[7009]: connect to 192.168.1.61 failed
Because of the ConnFailTimeout=10 setting in /etc/iscsi.conf both paths fail as
the controller failover takes about 45 - 60 seconds in the test.
Example 7-18 multipath -l during the controller failover
danube:~ # multipath -l
20003390012f2c829
[size=97 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [enabled][best]
\_ 2:0:2:0 sdb 8:16
\_ round-robin 0 [enabled]
\_ 2:1:2:0 sdc 8:32
danube:~ #
The queue_if_no_path setting /etc/multipath.conf ensures that IO will be queued
in this situation.
Example 7-19 /var/log/messages as controller failover finishes
Aug 3 13:40:36 danube kernel: iSCSI: bus 1 target 2 trying to establish
session to portal 0, address 192.168.1.125 port 3260group 1
Aug 3 13:40:36 danube kernel: iSCSI: bus 1 target 2 established session #3 to
portal 0, address 192.168.1.125 port 3260 group 1, alias danube-disk1
Aug 3 13:40:36 danube kernel: iSCSI: session iscsi_bus 1 target id 2 recv_cmd
cdb 0x28, status 0x2, response 0x0, senselen 18, key 06, ASC/ASCQ 29/01, itt
18716 to (2 1 2 0), danube-disk1
[failed]
[failed]
Chapter 7. TotalStorage DS300 installation
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