Syncmirror Without Metrocluster - IBM N Series Hardware Manual

partner 0c.18
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8.5.2 SyncMirror without MetroCluster

SyncMirror local (without MetroCluster) is basically a standard cluster with one or both
controllers mirroring their RAID to two separate shelves. However, if you lose a controller and
one of its RAID sets (plexes) during failover, the partner does not take over the other RAID set
(plex). Therefore, without MetroCluster, all of the same rules apply as for a normal cluster:
If controller A fails, partner B takes over.
If loop A (Plex0) on controller A fails, controller A continues operation by running through
loop B (Plex1).
If controller A fails and either loop A or loop B (Plex0/Plex1) fails, you cannot continue.
MetroCluster protects against the following scenario: If controller A fails and its SyncMirrored
shelves attached to loop A (Plex0) or loop B (Plex1) fail simultaneously, partner B takes over.
Partner B takes over the operation for partner A and its SyncMirrored plex on either loop A
(Plex0) or loop B (Plex1). See Figure 8-10.
Figure 8-10 MetroCluster protection
0c 1 2 FC:B 0 FCAL 15000 0/0
0a 1 7 FC:A 1 FCAL 15000 0/0
0a 1 12 FC:A 1 FCAL 15000 0/0
0a 1 8 FC:A 1 FCAL 15000 0/0
0c 1 3 FC:B 0 FCAL 15000 0/0
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Chapter 8. MetroCluster
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