External volumes must meet the Universal Volume Manager requirements.
When planning external volumes, note the following:
- You can use existing data
in an external volume after it is mapped to the local storage system, with these
restrictions:
- (VSP 5000 series) You must set the emulation type to OPEN-V when you map the volume.
- To perform host I/O operations, you must set an LU path from the target port to the mapped volume by using Device Manager - Storage Navigator, or a namespace for NVMe by using CCI.
- An external volume cannot be mapped to a DP pool that has DP-VOLs with the capacity saving function enabled. Capacity saving features are not supported for external storage.
- You cannot enable the capacity saving function on a DP-VOL from a DP pool that has pool volumes from external storage.
- The maximum or minimum
available capacity of an external volume depends on the emulation type you
specify when mapping the volume.
(VSP 5000 series) For more information, see Capacity requirements for volumes.
- You cannot access data stored in an external volume that exceeds the allowed maximum capacity. See the Maximum capacity of an external volume row in System requirements.
- Make sure that a mapped
external volume is accessed only from the local storage system.
- Make sure that a mapped external volume is not accessed from a host that is connected to the external storage system.
- Make sure that a mapped external volume is not manipulated by a copy function or any other functions of the external storage system.
- Accessing a mapped external volume from the external storage system requires that the volume mapping be disconnected first.
- External volumes that are reserved by a host cannot be mapped as internal volumes. To map these volumes, cancel the reserve settings, remove host access to the volumes, and then perform the mapping operation.
- Do not map multi-platform volumes of external storage systems as internal volumes.
- If an external storage
system that uses control unit path ownership is connected to the local storage
system, configure the external path to the primary controller in the external
storage system as the primary path.
Ownership is the exclusive right to control volumes. A controller that has ownership is called a primary controller. If the external path is connected to a controller that does not have ownership, and the path is configured as primary path, the ownership will be transferred, which might affect performance.
- A management LU cannot be
used as an external volume.
A management LU receives commands from an application because it controls or manages the application, and stores control information from the application. An example of a management LU is a Universal Xport LU. (A command device is not a management LU.)
Before performing the external volume mapping operation, perform one of the following operations on the external storage system:
- Delete the management LU from the port to be connected to the local storage system.
- Make sure that at least one LU is used for data storage and has a smaller LUN (LU number) than the LUN of the management LU. Also make sure that the data storage LU is set to the port connected to the local storage system.
- Use the security function and configure the access attribute of the management LU to prohibit read and write operations.
An external storage system that has a management LU might not be recognized by the local storage system.
- You cannot map an external volume whose capacity is smaller than the minimum capacity required for internal volumes.
- Before the settings of an external storage system are changed, mapping to volumes on the local storage system must be removed by selecting Disconnect External Volumes. After the external storage system settings are changed, volumes can be remapped. Unless external volumes are remapped, they cannot be used on the local storage system.
- If an LU path or a namespace on the NVM subsystem with an NVM subsystem port added for NVMe is configured on an internal volume mapped to an external volume, the external volume mapping cannot be deleted.
- Mapping cannot be deleted
for a volume used in a pair for the following programs:
- TrueCopy
- Universal Replicator
- ShadowImage
- Thin Image
- Global-active device
- Mapping cannot be deleted for an external volume configured as a pool volume.
- Mapping cannot be deleted for an external volume configured as a quorum disk.