IBM Storwize V7000, Introduction And Implementation Manual

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IBM Flex System V7000 Storage Node Introduction and Implementation Guide
9.4.2 1720 error
The 1720 error (event ID 050020) is the other primary error code of Remote Copy. Because
the term “System Partnership” implies that all involved virtualization systems are partners,
they must be able to communicate with each other. When a partner on either side stops
communicating, you see a 1720 error appear in your error log. According to official
documentation, there are no likely field replaceable unit breakages or other causes.
In practice, the source of this error is most often a fabric problem or a problem the network
path between your partners. When you receive this error, if your fabric has more than 64 HBA
ports zoned, you should check your fabric configuration for zoning of more than one HBA port
for each node per I/O group. One port for each node per I/O group associated with the host is
the recommended zoning configuration for fabrics. For those fabrics with 64 or more host
ports, this recommendation becomes a rule. You must follow this zoning rule or the
configuration is technically unsupported.
Improper zoning leads to SAN congestion, which can inhibit remote link communication
intermittently. Checking the zero buffer credit timer through IBM Tivoli Storage Productivity
Center and comparing its value against your sample interval might reveal potential SAN
congestion. Anytime a zero buffer credit timer is above 2% of the total time of the sample
interval, it is likely to cause problems.
Next, always ask your network provider to check the status of the link. If the link is okay, watch
for repetition of this error. It is possible in a normal and functional network setup to have
occasional 1720 errors, but multiple occurrences point to a larger problem.
If you receive multiple 1720 errors, recheck your network connection and then check the IBM
Flex System V7000 Storage Node partnership information to verify their status and settings.
Perform diagnostic tests for every piece of equipment in the path between the two systems. It
often helps to have a diagram showing the path of your replication from both logical and
physical configuration viewpoints.
If your investigation fails to resolve your Remote Copy problems, you should contact your IBM
support representative for a complete analysis.
9.5 Managing Remote Copy using the GUI
IBM Flex System V7000 Storage Node provides a separate function icon for copy service
management. There are two windows for managing Remote Copy, which are accessed
through the Copy Services function icon:
򐂰 Remote Copy
򐂰 Partnerships
As the name implies, these two windows are used to manage Remote Copy and the
partnership for the copy relationship.
9.5.1 Managing cluster partnerships
The Partnership window is used to manage a partnership between the mirroring clusters.
To access the Partnership window, click the Copy Services function icon and click
Partnerships (Figure 9-69).