Fibre Channel Link Failures - IBM Storwize V7000 Unified Problem Determination Manual

6. Ensure that proper bandwidth is given to iSCSI on the network.

Fibre Channel link failures

When a failure occurs on a single Fibre Channel link, the small form-factor
pluggable (SFP) transceiver might need to be replaced.
Before you begin
The following items can indicate that a single Fibre Channel link failed:
v The Fibre Channel status LEDs at the rear of the node canister
v An error that indicates a single port failed
378
Storwize V7000 Unified: Problem Determination Guide 2073-720
You do not need to enable PFC on the Storwize V7000 Unified system. Storwize
V7000 Unified reads the data center bridging exchange (DCBx) packet and
enables PFC for iSCSI automatically if it is enabled on the switch. In the
lsportip command output, the fields lossless_iscsi and lossless_iscsi6
show [on/off] depending on whether PFC is enabled or not for iSCSI on the
system.
If the fields lossless_iscsi and lossless_iscsi6 are showing off, it might be
due to one of the following reasons:
a. VLAN is not set for that IP. Verify the following checks:
v For IP address type IPv4, check the vlan field in the lsportip output. It
should not be blank.
v For IP address type IPv6, check the vlan_6 field in the lsportip output. It
should not be blank.
If the vlan and vlan_6 fields are blank, set the VLAN for the IP type
v
using Configuring VLAN for iSCSI.
b. Host flag is not set for that IP. Verify the following checks:
v For IP address type IPv4, check the host field in the lsportip output. It
should be yes.
v For IP address type IPv6, check the host_6 field in the lsportip output. It
should be yes.
v If the host and host_6 fields are not yes, set the host flag for the IP type
using the cfgportip CLI command.
c. PFC is not properly set on the switch.
If the VLAN is properly set, and the host flag is also set, but the
lossless_iscsi or lossless_iscsi6 field is still showing off, some switch
settings might be missing or incorrect.
Verify the following settings in the switch:
v Priority tag is set for iSCSI traffic.
v PFC is enabled for priority tag that is assigned to iSCSI CoS.
v DCBx is enabled on the switch.
Also check the appropriate documentation:
v Consult the documentation for enabling PFC on your specific switch.
v Consult the documentation for enabling PFC on Red Hat Enterprise
Linux (RHEL) and Windows hosts specific to your configuration.
You can divide the bandwidth among the various types of traffic. It is
important to assign proper bandwidth for good performance. To assign
bandwidth for iSCSI traffic, you need to first enable the priority flow control
for iSCSI.