IBM N Series, Hardware Manual

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IBM System Storage N series Hardware Guide
If you use SAS Shelves (EXN3000 and EXN3500), you must use FibreBridges. Starting with
Data ONTAP 8.1, EXN3000 (SAS or SATA) and EXN3500 are supported on Stretch
MetroCluster (and Fabric MetroCluster) through SAS FC bridge (FibreBridge).
The FibreBridge runs protocol conversion from SAS to FC and enables connectivity between
Fibre Channel initiators and SAS storage enclosure devices. This process enables SAS disks
to display as LUNs in a MetroCluster fabric. You need a minimum of four FibreBridges
(minimum is two per stack) in a MetroCluster environment, as shown in Figure 8-6.
Figure 8-6 Cabling a Stretch MetroCluster with FibreBridges and SAS Shelves
8.4 Fabric Attached MetroCluster
Fabric Attached MetroCluster, which is sometimes called Fabric MetroCluster , is based on
the same concept as Stretch MetroCluster. However, it provides greater distances (up to
100 km) by using SAN Fabrics. Both nodes in a Fabric MetroCluster are connected through
four Fibre Channel switches (two fabrics) for high availability and data mirroring. There is no
direct connection as with Stretch MetroCluster. The nodes can be placed in different
locations. Since Data ONTAP 8.0, Fabric Metro Clusters require dedicated fabrics for internal
connectivity (back-end traffic and FC/VI communication). It does not support sharing this
infrastructure with other systems.
Minimum of four FibreBridges are required when SAS Shelves (EXN3000 and EXN3500) are
used in a MetroCluster environment.