Home > Storage > Unity XT > Storage Admin > Dell Unity: NAS Capabilities > Locking and folder rename policy
Starting with OE version 4.1, the locking and folder rename policies can be configured on multiprotocol file systems. These settings allow the administrator to control the wanted behavior since locking and folder renaming behave differently depending on the protocol. Both settings can be configured during file system creation or afterwards.
Range locks allow hosts to lock a byte range of a file. These locks can be shared locks (writes denied) or exclusive locks (reads/writes denied). Each protocol leverages either mandatory or advisory locking. For mandatory locks, any IO to the locked range is denied. For advisory locks, it is the client’s responsibility to check for a lock and even if a lock is detected, it can disregard it and perform IO anyway. The table below shows the locking semantics and mechanisms for NFSv3, NFSv4, and SMB.
Protocol | Advisory/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 must be configured for the wanted behavior on multiprotocol file systems. The protocol that is used and the locking policy setting determines whether a lock prevents IO:
The table below 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 |
To configure the locking policy during file system creation, open the Advanced File System Settings menu as shown below.
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. This is because SMB opens the entire path but NFS and FTP leverages file handles instead. Due to the differences between protocols, the Folder Rename Policy allows the storage administrator to configure the wanted 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:
To configure the folder rename policy on an existing file system, browse the File System Properties à Advanced