The ProtecTIER Metadata Planner enables the field engineer to understand how many  metadata file systems are required to support a repository of a certain size and the size of the  metadata file systems.  There are other utilities in the ProtecTIER Planner, such as upgrading from a previous version  (with the import of historical user data), and customizing any disk performance information  based on unique user scenarios when planning performance.  For more information about capacity planning for a TS7650 Appliance environment, see  IBM  System Storage TS7600 with ProtecTIER Version 3.3 , SG24-7968. The ProtecTIER Planner should be used for capacity and performance planning while  manually adapting it to a many-to-many environment at an early stage before the ProtecTIER  deployment. The parameters to be considered are the same ones that are used in any  replication deployment:  Independent from the back-end storage subsystem, some general guidelines indicate how to  lay out your storage for optimal usage of ProtecTIER. Depending on whether you plan to deploy a small or large ProtecTIER gateway solution, be  aware of certain limits and effects. All storage subsystems come with multiple controllers. So, you must use at least two LUNs to  distribute them across both controllers of a storage subsystem. All IBM Storage Subsystems are based on standard hardware. For example, the IBM System  Storage DS8000fi is based on the IBM System p architecture, and the IBM Storwizefi Family  and SAN Volume Controller are based on the IBM System x architecture. With these  architectures, the controller nodes of the storage subsystems tend to have multiple  processors driving the input/output (I/O), and multiple cores per processor.  To use all of these resources, you must have multiple LUNs per controller at the same time.  For example, with the IBM Storwize Family and SAN Volume Controller, you must have at  least four arrays per controller to ensure the optimal usage of all computing cores. Based on these calculations, assume that a minimum number of eight LUNs enables an  optimal usage of the available resources. These are some more general assumptions. Your  individual system might be fine with fewer than eight LUNs if sizing and planning were done  for your individual requirements. ProtecTIER uses a special method to write data to disk. ProtecTIER writes data to disk by  creating data in or appending data to the repository structure. These are the two principal  modes of operation. Data that can be expired from a ProtecTIER perspective is not  overwritten. It is deleted by the maintenance processes and is reshaped by the defragger  practices before it is used again by write or append operations.  Chapter 7. Back-end storage overview  103 7.3 Dependencies from a ProtecTIER view 7.2 Dependencies from a back-end storage subsystem view GLYPH<SM590000> Time frames. Backup and replication windows or concurrent operation. GLYPH<SM590000> Network bandwidth. Available and required between the PT nodes on the grid. GLYPH<SM590000> System workload. Both local backup and replication, including incoming and outgoing.