Home > Workload Solutions > Oracle > White Papers > Dell PowerMax 2500 and 8500 Best Practices for Mission Critical Oracle Databases > Masking Views
PowerMax uses masking views to determine which storage devices are visible to hosts. A masking view contains a Storage Group (SG), Port Group (PG), and Initiator Group (IG). When a masking view is created, the devices in the SG are made visible to the appropriate hosts by their initiators in the IG, over the ports in the PG.
When changes are made to any of the masking view components, they automatically update the masking view and derived connectivity. For example, adding devices to the SG automatically makes the new devices visible to the host[1] through the initiators and ports in the masking view.
A storage group (SG) contains a group of devices that are managed together. Also, a SG can contain other SGs, making them child SGs, while the top-level SG becomes the parent SG. In this case, manage the devices either by using any of the child SGs directly or by using the parent SG so that the operation affects all the child SGs. For example, use the parent SG for the masking view, remote replication, or to create consistent snapshots of the whole database. Use the child SGs to restore and recover only the database data without overwriting the database transaction log.
If using Oracle container database feature (CDB), also consider the following:
For more details on CDB and PDB considerations, see the section Oracle multitenant container database (CDB).
An initiator group (IG) contains a group of host initiators’ (server HBA ports) World Wide Names (WWNs) to which storage devices are mapped. Also, an IG can contain other IGs, making them child IGs, while the top-level IG becomes the parent IG.
A parent/child IG deployment is useful when the database is clustered. Each child IG contains the initiators from a single server, and the parent IG aggregates all the servers. When the masking view is created, the parent IG is used. When a cluster node is added or removed from the cluster, the masking view does not change. Only the parent IG is updated by adding or removing the child IG that matches the cluster node that is being added or removed.
In Unisphere, IGs, or child-IGs are called Hosts, and parent-IGs are called Host Groups.
A port group (PG) contains a group of targets (storage front-end ports). When placed in a masking view, PGs are the storage ports through which the devices in the SG are accessed.
Because the switch zone sets determine physical connectivity, for simplicity of management, it is recommended to include all the storage ports that the database use in the PG. The switch zone sets determine the specific path relationships between the PG ports and IG initiators.
For environments that are not mission critical, it is sufficient to add all the database devices into a single SG and to use a single masking view. The following guidelines apply to high-performance, mission critical databases in which data and log SGs are separated to allow backup and recovery by using storage snapshots and more granular performance monitoring.
In this scenario, data_sg and redo_sg are joined under a parent SG, while FRA is in its own SG. The following table shows that there are two masking views for the database and one for the cluster or Grid Infrastructure.
When using Oracle container (multitenant) databases, masking views are created for the CDB$ROOT and PDB$SEED ASM disk groups. For more details on CDB and PDB considerations, see the section Oracle multitenant container database (CDB).
Masking view | Storage Group | Child SGs | Initiator Group | Child IGs | Port Group |
App1_DataRedo | App1_DataRedo | App1_Data, App1_Redo | App1_hosts | Host1, Host2 | PMAX_304_PG1 |
App1_FRA | App1_FRA | (none) | (same as above) | (same as above) | (same as above) |
Grid | Grid | (none) | (same as above) | (same as above) | (same as above) |
cdbroot | cdbroot_sg | (none) | (same as above) | (same as above) | (same as above) |
pdbseed | pdbseed_sg | (none) | (same as above) | (same as above) | (same as above) |
The following are benefits gained from such a design: