Troubleshooting Ip Mirroring - HP Open View Installation And Maintenance Manual

Troubleshooting IP mirroring

A description of common IP mirroring situations follows:
Continuous Access Storage Appliance Installation and Maintenance Guide
I/O stops on the hosts after disconnecting the InterLink and MirrorLink.
If you disconnect the InterLink and MirrorLink, the appliance loses all connectivity to the
mirror site and enters arbitration. The appliance cannot enter arbitration until all I/O times
out. To prevent I/O from timing out, increase the value of the I/O time–out parameter (for
example, 10 minutes).
The IP mirror disconnects and I/O stops on the hosts when one MirrorLink is down.
For synchronous IP mirrors, this occurs because the active MirrorLink is saturated. The
I/O must wait for network scheduling. To prevent I/O from timing out, increase the value
of the I/O time–out parameter (for example, 10 minutes).
When a change occurs to the MirrorLink (either failure or restore), SMS may not
detect the change for the mirror node immediately.
If there is a large number of mirrors resynchronizing, there may be a delay in updating the
link state as the appropriate caches are updated for each mirror (specifically, the mirror
cache, LUN cache, consistency set cache, and node cache). To update the status of the
nodes immediately, enter the following command in sanosadmin:
mod cache -name all -refresh
See "mod cache" on page 171 for more information about this command.
After deleting an IP mirror, sometimes it is still visible from the remote appliance.
This occurs if you delete the IP mirror when the mirror site (remote appliance) is down. To
prevent this situation, ensure the mirror site is up before you delete the IP mirror.
If the local and remote system administrators create a mirror using the same LUNs
at exactly the same time (each thinks it is the source), the user interface indicates that
both mirrors were successful, but only one mirror was.
It is unlikely that this situation will occur. However, HP recommends that the system
administrator notify other system administrators before performing an IP mirror request.
In a future release, the appliance's user interface will reflect that only one mirror was
successful.
Explain the most efficient way to create and maintain IP mirrors for multiple
applications.
Create a consistency set for each application. For example, your Oracle database uses
LUNs 1, 2, and 3; your web applications use LUNs 4 and 5. Create two consistency sets,
named oracle and webapps, for example. Assign LUNs 1, 2, and 3 to the oracle
consistency set; assign LUNs 4 and 5 to the webapps consistency set. Write ordering is
maintained within each group, ensuring data consistency on the remote site.
IP Mirroring
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