Chapter 2. System overview 23
However, the write cache is still assigned to a maximum of 12 GB and compression cache to 
a maximum of 34 GB. The remaining installed cache is used as read cache (including 
allocation for features, such as FlashCopy, Global, or Metro Mirror).
2.5.6  Clustered system
A clustered system consists of 1 - 4 pairs of nodes. All configuration, monitoring, and service 
tasks are performed at the system level, and the configuration settings are replicated across 
all node canisters in the clustered system. To facilitate these tasks, one or two management 
IP addresses are set for the system.
A process is provided to back up the system configuration data to disk so that the clustered 
system can be restored if a disaster occurs. This method does not back up application data, 
only the IBM Storwize V7000 system configuration information.
For the purposes of remote data mirroring, two or more clustered systems (IBM Spectrum 
Virtualize systems starting from software V7.1) must form a partnership before creating 
relationships between mirrored volumes.
One node is designated as the configuration node canister. It is the only node that activates 
the system IP address. If the configuration node canister fails, the system chooses a new 
configuration node and the new configuration node takes over the system IP addresses.
The system can be configured by using either the IBM Spectrum Virtualize GUI-based 
management software, the CLI, or through an application, such as IBM Spectrum Control, 
that uses the IBM Storwize V7000 Common Information Model object manager (CIMOM).
Note: When installing cache in your IBM Storwize V7000 Gen2+ and upgrading to V8.1, 
the error message “1199 Detected hardware needs activation” appears in the GUI event 
log with an associated error code 0x841 in CLI. Run the command chnodehw <node_id> 
-force for each affected canister in sequence or perform the fix procedure by using the 
GUI.
System configuration backup: After backing up the system configuration, save the 
backup data outside of the SAN. If you cannot access the IBM Storwize V7000, you do not 
have access to the backup data if it is on the SAN.
Important: IBM Storwize V7000 V6.3 introduced the layer parameter. It can be changed 
by running chsystem by using the command-line interface (CLI). The default is the storage 
layer. You must change it to replication if you need to set up a copy services relationship 
between the IBM Storwize family and IBM SAN Volume Controller.