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IP Mirroring
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Continuous Access Storage Appliance Installation and Maintenance Guide
Common resynchronization issues
A description of common resynchronization issues follows:
■
After you power off the resynchronizing node, synchronous IP mirrors disconnect.
Temporarily disconnecting the IP mirrors starts resynchronization on the new
resynchronizing node, (the peer node that is working). Resynchronizing ensures that the
data on the source and target LUNs of the mirrors is current.
■
After you reboot the mirror nodes, synchronous IP mirrors continually disconnect
and resynchronize.
Synchronous IP mirrors disconnect when the network is saturated with I/O (regular
requests and resynchronizations) or when the mirrors are grouped in a consistency set. To
prevent the mirrors from disconnecting, limit the number of simultaneous
resynchronizations to three or four. Do not use a consistency set for synchronous IP
mirrors unless it is necessary.
■
After you disconnect the cable between an external storage array and the
resynchronizing node, synchronous IP mirrors disconnect.
The resynchronizing node cannot perform a resynchronization if it does not have a
physical connection to the storage array. However, normal I/O (non-resynchronizing I/O)
continues. After you connect the node and the storage array, the node resumes its role as
the resynchronizing node and resynchronization resumes.
■
When you set the value of the maxresyncthreads parameter to 1 and create several IP
mirrors, you only see one mirror on the remote appliance when the mirror is
resynchronizing.
The resynchronizing thread communicates with the mirror node when defining an IP
mirror. If you only define one resynchronization thread, that thread must define the mirror
and complete the resynchronization before defining the next mirror. To avoid this
situation, do one of the following:
— Create one IP mirror and wait for the resynchronization to complete before creating
the next IP mirror.
— Change the value of the maxresyncthreads parameter to the number of IP mirrors you
are creating.