•The attributes that are set for the external volume originally on the external storage system side (such as the port security, the LUN security, the Volume Retention Manager attributes, and so on) are not kept, when the external volume is mapped as an internal volume. If the original attributes are required to be set, set the attributes on the mapped external volume from the local storage system side.
•For the external volume, for which the Cache Mode is set to Disable, the bind mode for the Cache Residency Manager operation is not available.
•If you use the mapped external volume for the Cache Residency Manager operation and set the bind mode, the cache of twice as much capacity as the user data is required for the Cache Residency Manager operation.
Creating LUSE Volume Guidelines
•Do not combine LDEVs of multiple external storage systems to create a LUSE volume. The LDEVs in the same external storage system can only be used to set the LUSE volumes.
When you combine LDEVs of multiple external storage systems to create a LUSE volume, the following problems will occur:
◦If a LUSE volume consists of multiple external storage systems and one external storage system volume has lower performance than the other storage system volumes, the lower performance of the volume affects the performance of the LUSE volume.
◦When an external storage system volume that is part of a LUSE volume is blocked, data reliability of the LUSE volume will deteriorate because the LUSE volume has both accessible area and inaccessible area from a host.
◦When you disconnect an external volume or resume the use of an external volume, you need to perform the operation at the same time on all the external volumes that are components of the LUSE volume.
•The mapped volumes that have different cache mode settings cannot be used to create one LUSE volume.
42 Preparing for XP External Storage Operations