System layers

The system layer affects how the system interacts with a SAN Volume Controller system and other external Lenovo V series systems.

An IBMLenovo V series system is in either the replication layer or the storage layer.

Differences between the storage layer and the replication layer

Comparison of storage layer and replication layer systems 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 SAN Volume Controller system.
  • The system cannot use another Lenovo V series 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 SAN Volume Controller system.
  • The system cannot provide external storage for a replication-layer system or a SAN Volume Controller system.
  • The system can use another Lenovo V series system that is configured with storage-layer as external storage.

A Lenovo V series system is in the storage layer by default, but the layer can be changed. For example, you might want to change a Storwize V7000 system to a replication layer to complete Global Mirror or Metro Mirror replication with a SAN Volume Controller system.

Changing the layer of a Lenovo V series system

To change the storage layer of an existing Storwize 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 Chanel (FC) connections to another Lenovo V series or SAN Volume Controller 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 a Lenovo V series system.
  • No system partnerships can be defined.
  • No Lenovo V series system can be visible on the SAN fabric.
To change the layer of a system, follow these general steps:
  1. Use the svc_lssystem.html#chsystem command to check the current system layer.
  2. Configure SAN zoning so that the system whose layer you are changing is not visible to any other system.
  3. Ensure that all other configuration requirements are met.
  4. Run the svc_requestdiscovery_21ifux.html#lsvc_requestdiscovery_21ifux command to ensure that the system detects any fabric changes that were done in step #svc_systemlayer/configreq.
  5. Enter the one of the following commands to switch the system to the appropriate layer.
    • To switch to the replication layer, enter the chsystem command.
    • To switch to the storage layer, enter the chsystem command.
  6. If the SAN configuration was changed in step #svc_systemlayer/configsanzoning, restore the normal SAN configuration.
  7. Run the svc_requestdiscovery_21ifux.html#lsvc_requestdiscovery_21ifux command to update the list of MDisks.
Parent topic: Technical overview