By Yadagiri Rajaboina , Vinayak Prasad Karne | Published June 26, 2018
In general, the storage area network (SAN) applications on Fibre Channel (FC) switches periodically probes the host FC host bus adapter (HBA) ports for diagnostic data. In large data centers, the collected diagnostic data helps SAN support teams for monitoring and troubleshooting the FC HBAs. Read Diagnostic Parameters (RDP) is a FC Extended Link Service (ELS) introduced with the FC-LS-3(T11) specification. The RDP ELS (command code:0x18) provides a mechanism to collect the information that can be used for the diagnosis of link or port related errors, or degraded conditions associated with the designated FC port. Some of the information includes port speed, link error status, port name, and Small Form-Factor Pluggable (SFP) information (such as temperature, voltage, and so on). This data is useful in predictive analysis to identify the faulty HBAs quickly.
The RDP supported FC switches transmits the RDP ELS request payload to the host HBA port and the host HBA port responds to the same request, as shown in Figure 1.
The reply from the host HBA can be accept (LS_ACC) with diagnostic data or reject (LS_RJT) ,if the port does not support the RDP request. Without support for responding to the RDP ELS request, the IBM® AIX® Fibre Channel (FC) / Fibre Channel over Ethernet (FCoE) device drivers stack rejects the RDP ELS request and AIX operating system logs the error with the errpt command with sense data similar to:
ECCE4018 0309105518 T S fcs0 SOFTWARE PROGRAM ERROR
0000 0020 0000 068A 0002 0005 0000 217B 0000 004B 0006 2500 1000 0090 FA02 F5E4
1800 0000 00FF FC06 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
The capability to respond to RDP ELS is added to IBM AIX FC and FCoE device drivers from the following AIX releases:
The AIX FC/FCoE device driver stack, responds to RDP ELS requests with the following ELS descriptors:
The following sections explain RDP ELS related commands on Brocade and Cisco FC switches.
The Brocade FC switches with RDP ELS supported fabric OS level sends an RDP ELS request to the connected host FC ports periodically. The value for the RDP polling cycle can be tuned from 1 hour to 24 hours. The RDP polling cycle value to ‘0’ stops sending RDP ELS requests to host HBA ports. Figure 2 shows the current RDP polling cycle value.
Figure 3 explains how to modify the RDP ELS interval to 2 hours.
The Brocade Fabric OS CLI commands, sfpshow and portshow shown in Figure 4 and Figure 5 sends an RDP ELS request to collect diagnostics information of the host HBA port. In these examples, the host FC HBA port is connected to port number: 0 on the FC switch.
On RDP capable Cisco switches, the show rdp command sends an RDP ELS request to collect diagnostics information of the host HBA port. Figure 6 shows the collection of such data for the host port with the N_Port ID: 0xaa0020.
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