IBM N Series - Syncmirror Without Metrocluster

Chapter 8. MetroCluster 117
partner 0a.28 0a 1 12 FC:A 1 FCAL 15000 0/0 137104/280790184
partner 0a.24 0a 1 8 FC:A 1 FCAL 15000 0/0 137104/280790184
partner 0c.19 0c 1 3 FC:B 0 FCAL 15000 0/0 274845/562884296
8.5.2 SyncMirror without MetroCluster
SyncMirror local (without MetroCluster) is 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 following 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 that are 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), as shown in Figure 8-10.
Figure 8-10 MetroCluster protection