Data LUN configuration

You can configure the SAN so that all data LUNs are available to all clients (known as a uniform configuration) or so that only a subset of data LUNs are available to some clients (known as a nonuniform configuration). In nonuniform configurations, a client must be able to access all LUNs in any storage pool that has been used or can be chosen by a fileset that is used by that client.

If a client tries to read or write data on a LUN that it cannot access, SAN File System returns an I/O error to that client. If the client performs a file-system operation that only involves metadata (such as changing a directory, or listing or creating files), SAN File System does not return an I/O error because the operation does not involve the data LUN.

The active policy determines which storage pool is selected when a new file is created. In a nonuniform configuration, the policy must ensure that a newly-created file is allocated to a storage pool that is accessible to the clients that need the file. When you change the active policy, the new policy must meet this consistency property.

Note: There is no automatic consistency check for a nonuniform configuration; however, when a client identifies itself to a metadata server, the metadata server inspects the client volume list to ensure that no incomplete storage pools are visible to the client. If an incomplete storage pool is visible, the metadata server logs an error in the metadata server log.

Parent topic: Clients

Parent topic: Planning the client configuration

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IBM TotalStorage SAN File System v2.2