The system layer affects how the system interacts with a system
and other external systems that run IBM Spectrum Virtualize software.
Systems that run IBM Spectrum Virtualize
software can either be in the replication layer or the storage layer.
Differences between the storage layer and the replication layer
This table compares the characteristics and requirements of storage layer and replication
layer systems.
Table 1. Comparison of storage layer and replication layer systems
| Storage layer |
Replication layer |
- The system can complete Metro Mirror and Global Mirror replication with other
storage-layer systems.
- The system can provide external storage for replication-layer systems or a system.
- The system cannot use another Storwize® family or FlashSystem family system that is
configured with storage-layer as external storage.
|
- The system can complete Metro Mirror and Global Mirror replication with other
replication-layer systems or a system.
- The system cannot provide external storage for a replication-layer system or a system.
- The system can use another Storwize family or FlashSystem family system that is
configured with storage-layer as external storage.
|
An Storwize family or FlashSystem family system is in the
storage layer by default, but the layer can be changed. For example, you might want to change a
system to a replication layer to complete Global Mirror or Metro Mirror replication with a system.
Changing the layer of an Storwize family or FlashSystem family system
To change the storage layer of an existing system with internal storage before you add a
second system into the SAN zone, you do not need to stop I/O operations.
However, if the system has Fibre Channel (FC) connections to another Storwize family, FlashSystem family, or system in the SAN fabric, I/O
operations must be stopped temporarily. In this scenario, the FC ports must be disabled (for
example, by unplugging all the FC ports, changing zoning, disabling switch ports) before you change
the system layer. Then, you must re-enable the FC ports.
Before you change the system layer, the following conditions must be met:
- No host object can be configured with worldwide port names (WWPNs) from an Storwize family or FlashSystem family system.
- No system partnerships can be defined.
- No Storwize family or FlashSystem family system can be visible
on the SAN fabric.
To change the layer of a system, follow these general steps:
- Use the lssystem command
to check the current system layer.
- Configure SAN zoning so that the system whose layer you are changing
is not visible to any other system.
- Ensure that all other configuration requirements are met.
- Run the detectmdisk command to ensure that the system detects any fabric
changes that were done in step 3.
- Enter the one of the following commands to switch the system to the appropriate layer.
- If the SAN configuration was changed in step 2, restore the normal SAN configuration.
- Run the detectmdisk command to update the list of MDisks.