Skip to main content
NetApp Knowledge Base

What are the effects of file locking on NFSv3 and CIFS clients?

Views:
2,990
Visibility:
Public
Votes:
0
Category:
ontap-9
Specialty:
nas
Last Updated:

 

Applies to

  • ONTAP 9
  • Data ONTAP 8 7-mode

Answer

Note: There are more complex scenarios like multiprotocol access (CIFS and NFS) which are not covered here.

  • Locks set by Network File System (NFS) clients are not enforced
    • A client may gain access to a locked file, or to part of a locked file, depending on whether the client checks for and observes the lock
    • This only applies to NFSv3 using NLM, but NFSv4 has a mandatory locking infrastructure
  • Locks set by CIFS/SMB clients are enforced
    • The locks affect clients, whether or not the clients check for the locks.
    • If a lock exists, the client is denied the type of access according to the lock.
  • If running the dump command on Data ONTAP 8 7-mode, it will ignore the file lock to finish the dump or NDMP backup.
How does ONTAP keep track of locks?
  • Lock Manager (LMGR) is an ONTAP subsystem that implements file locking to manage concurrent access.
    • It keeps track of which files are open and which locks are granted.
    • This is handled in the Data/WAFL layer of ONTAP
  • Each node on an ONTAP 9 cluster has its own lock manager running that manages the volumes located on aggregates owned by that node.
    • Note: In 7-mode this is per controller
  • To accomplish these tasks, a series of memory structures (objects) are allocated to the lock manager; the amount of these structures depends on the amount of memory installed on the storage controller and is fixed.
NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.