content_image/998733.jpg
External LUs can have one of the following modes: 

GLYPH<SM590000> Unmanaged 

External MDisks are discovered by the system as unmanaged MDisks. An unmanaged MDisk is not a member of any storage pool. It is not associated with any volumes, and has no metadata stored on it. The system does not write to an MDisk that is in unmanaged mode, except when it attempts to change the mode of the MDisk to one of the other modes. 

GLYPH<SM590000> Managed 

When unmanaged MDisks are added to storage pools, they become managed. Managed mode MDisks are always members of a storage pool, and their extents contribute to the storage pool. This mode is the most common and normal mode for an MDisk. 

GLYPH<SM590000> Image 

Image mode provides a direct block-for-block translation from the MDisk to a volume. This mode is provided to satisfy the following major usage scenarios: 

– Virtualization of external LUs that contain data that was not written through the IBM SAN Volume Controller. 

– Exporting MDisks from the IBM SAN Volume Controller after migration of volumes to image mode MDisks. 

## Listing external MDisks 

External MDisks can be managed through the External Storage pane, which is accessed by clicking Pools → External Storage  (see Figure 6-28). 

<img src='content_image/998733.jpg'>

To list all MDisks visible by the system with the CLI, use the lsmdisk command without any parameters. If required, output can be filtered to include only external or only array type MDisks. 

## Assigning MDisks to pools 

Add Unmanaged  MDisks to an existing pool or create a pool to include them. If the storage pool does not exist, follow the procedure that is described in 6.1.1, “Creating storage pools” on page 216. 

Figure 6-29 on page 234 shows how to add selected MDisk to a storage pool. Click Assign under the Actions menu or right-click the MDisk and select Assign . 

