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The locking and folder rename policies can be configured on multiprotocol file systems. These settings allow the administrator to control the behavior since locking and folder renaming behave differently depending on the protocol.
Range locks allow hosts to lock a byte range of a file. These locks can be shared locks (denies writes) or exclusive locks (denies reads and writes). Each protocol implements either mandatory or advisory locking. For mandatory locks, any I/O to the locked range is denied. For advisory locks, it is the responsibility of the client to check for a lock and even if a lock is detected, it can disregard it and perform I/O anyway. Table 10 shows the locking semantics and mechanisms for NFSv3, NFSv4, and SMB.
Protocol | Advisory or mandatory | Mechanism |
NFSv3 | Advisory | Separate protocol (NLM) |
NFSv4 | Advisory or mandatory (default) | Embedded in the protocol |
SMB | Mandatory | Embedded in the protocol |
Due to the differences in the protocol specifications, the locking policy can be configured to control the behavior on multiprotocol file systems. The protocol that is used and the locking policy setting determines whether a lock prevents I/O:
Table 11 also shows which locks are honored for each protocol and locking policy setting in a chart format.
Protocol | Mandatory (default) | Advisory |
NFSv3 | SMB + NFSv4 | None |
NFSv4 | SMB + NFSv4 | None |
FTP | SMB + NFSv4 | None |
SMB | SMB + NFSv4 | SMB |
Figure 25 shows how to configure the locking policy on a file system.
According to the SMB protocol specifications, renaming any directory that is in the path of an open file is prohibited. For example, if C:\Folder1\Folder2\Folder3\File1.txt is opened by an SMB client, other clients are prevented from renaming any of the folders in the path leading up to File1.txt.
Clients using NFS or FTP do not have the same restriction because SMB opens the entire path while NFS and FTP leverage file handles instead. Due to the differences between protocols, the folder rename policy allows the storage administrator to configure the behavior on multiprotocol file systems. The folder rename policy settings are only invoked when attempting to rename a folder in a path of an open file. Renaming folders that do not have any open files in the path are always allowed.
The folder rename policy can be configured to:
Figure 26 shows how to configure the folder rename policy on a file system.