HP StorageWorks Storage Mirroring application notes Guidelines for networking and failover (T2558-96063, February 2008)

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This document also discusses other networking topics related to failover, including how to view name
caches and the Address Resolution Protocol (ARP) cache to troubleshoot. Additionally, common questions
such as how failover affects domain controllers and how to fail over Internet Protocol (IP) addresses to
remote targets are addressed.
Understanding Storage Mirroring failover and failback
Storage Mirroring failover
When Storage Mirroring failover occurs, the following events take place. (Depending on the failover
options selected, the events listed may not occur or may occur in a different order.)
• The pre-failover script runs.
• The specified source IP addresses are added to the target network adapters.
• An unsolicited ARP is sent to inform the network segment of the change in IP address-to-Media Access
Control (MAC) address mappings.
• The source's DNS host name is added to the system as a NetBIOS name. First Storage Mirroring checks
the hosts file and uses the first name there. If there is no hosts file, Storage Mirroring uses the first name
in DNS. (Although, the first name in DNS may not always be the same each time the DNS server is
rebooted.) Lastly, if there is no DNS server, Storage Mirroring uses the Failover Control Center monitor
name.
NOTE: If the DNS host name you want added to the system is not being used, you will need to
reconfigure DNS so that only one host entry is available for the monitored IP address. If other names need
to resolve to that server, add alias records for those entries.
• The Microsoft Networking Client updates the WINS server, associating the source's host name as
returned by DNS with the target's primary IP addresses.
• The source's host Service Principal Names (SPNs) are removed from the source computer account and
added to the target computer accou
• The post-failover script runs.
Any other actions beyond the scope of these events that are required for successful failover must be
scripted and
cuted in the pre-failover or post-failover scripts. Ensuring that all clients will be able to access the source
after failover often requires failover scripting to update the name resolution servers.
Storage Mirroring failback
When Storage Mirroring failback occurs, the following events take place. (Depending on the failback
options selected, the events listed may not occur or may occur in a different order.)
• The pre-failback script runs.
• The source’s IP addresses are removed from the target’s network adapters.
• An unsolicited ARP is sent to inform the network segment of the change in IP address-to-MAC address
mappings.
• The source’s DNS name is removed.
• The Microsoft Networking Client updates the WINS server by tombstoning the source’s entry.
• The source host SPNs are removed from the target computer account and added to the source computer
account.
• The post-failback script runs.
• The source post-failback script runs.
Any other actions beyond the scope of these events that are required for successful failback must be
scripted and executed in the pre-failback or post-failback scripts.