Storage Cluster; Figure 73 Storage Cluster - Fujitsu ETERNUS DX S5 Series Design Manual

3. SAN Functions
Stable Operation

Storage Cluster

Storage Cluster is a function that allows continuous operations by using redundant connections to two ETERNUS
AF/DX storage systems so that even if the Primary storage fails, operations are switched to the Secondary
storage. Operations can continue without stopping access from the server if there are unexpected problems or if
the ETERNUS DX is in an error state due to severe failures.
Volumes that are accessed from business servers remain accessible with the same drive or mount point even
after a switchover of the ETERNUS AF/DX. Transparent access from business servers is possible even after a
switchover of the ETERNUS AF/DX. Reallocating volumes or switching mount points is not required.
Storage Cluster is set for each logical volume. A paired configuration for the target volume is created by
mirroring between ETERNUS AF/DX storage systems.
If a failover occurs during operation, a link down occurs in the CA port on the Primary storage, and the Secondary
storage takes over the information and a link up occurs on its own CA port. A maximum of 10 seconds is required
for the automatic switchover, but operations can continue with the server's I/O retry.
To use Storage Cluster, the ETERNUS SF Storage Cruiser Storage Cluster option is necessary.
Figure 73 Storage Cluster
ETERNUS AF/DX
For Storage Cluster settings, create TFO groups that include target volumes (TFOV), and specify the connection
configuration and the policy for each group.
TFOVs are mirrored and maintained equally as a pair in the Primary storage and the Secondary storage. Because
mirroring between storage systems is performed with a synchronous remote copy technology, the copy path
setting must also be configured in addition to the Storage Cluster-related settings.
Business server
SAN
I/O
Failover
CA
Device
failure
Primary storage
142
LAN
Storage Cluster
controller
CA
ETERNUS AF/DX
Secondary storage
Design Guide