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

Storage Mirroring Guidelines for networking and failover application notes 15
When Storage Mirroring is installed, the HP ARP Responder device driver is installed and set to a startup
type of demand (Windows 2000/2003) or manual (Windows NT 4.0). Storage Mirroring uses the HP
ARP Responder to broadcast an unsolicited (gratuitous) ARP when failover occurs. The unsolicited ARP
forces the systems on the same physical network to update their ARP caches with an entry associating the
source IP address with the target adapter's MAC address. The following event will be created in the
target's Application Event Log when the unsolicited ARP is broadcast:
Event ID: 5400
Source: Storage Mirroring
Type: Information
Description: Broadcasted new MAC address [target adapter MAC address] for IP address [source IP
address].
The
arp -a command can be used to see the ARP cache on a system for troubleshooting purposes.
Confirming Storage Mirroring failover
When Storage Mirroring executes a failover, it makes entries in the Storage Mirroring logs, the Windows
Event Log, and will generate an SNMP trap (if the SNMP component is installed). Operating system
commands can also be used to show that the appropriate name and IP address changes have been made.
The following messages are logged in the target's Storage Mirroring log file when failover occurs:
05/01/200213:34:14.5230101Failover in progress!!!
05/01/200213:34:44.2860700001Failover complete for SERVER1
A number of entries will be made in the Application Event Log as well:
Event ID: 5100
Source: Storage Mirroring
Type: Information
Description: Failover completed for [source computername]
Event ID: 5101
Source: Storage Mirroring
Type: Information
Description: IP address [source IP address] with subnet mask [source subnet mask] was added to target
machine's [target adapter name] adapter.
If the SNMP service and the Storage Mirroring SNMP component are installed, the target will generate the
following SNMP trap when failover occurs:
Trap: DttrapFailoverInProgress
Description: Failover is occurring.
The
nbtstat -n command can be used to verify that the source's name is successfully added to the target
after failover. This command shows the names registered on the local system. Following is a sample that
shows
nbtstat -n output on the target server CALLISTO before and after failover of the source server
GANYMEDE (in the JUPITER domain).
Before Failover
D:\>nbtstat -n
TS:
Node IpAddress: [172.16.137.31] Scope Id: []
NetBIOS Local Name Table
Name Type Status
-------------------------------------------
CALLISTO <00> UNIQUE Registered
JUPITER <00> GROUP Registered
CALLISTO <20> UNIQUE Registered
JUPITER <1E> GROUP Registered
INet~Services <1C> GROUP Registered
IS~callisto....<00> UNIQUE Registered