Reasons ONTAP invalidates BranchCache hashes

Contributors

Understanding the reasons why ONTAP invalidates hashes can be helpful as you plan your BranchCache configuration. It can help you decide which operating mode you should configure and can help you choose on which shares to enable BranchCache.

ONTAP must manage BranchCache hashes to ensure that hashes are valid. If a hash is not valid, ONTAP invalidates the hash and computes a new hash the next time that content is requested, assuming that BranchCache is still enabled.

ONTAP invalidates hashes for the following reasons:

  • The server key is modified.

    If the server key is modified, ONTAP invalidates all hashes in the hash store.

  • A hash is flushed from the cache because the BranchCache hash store maximum size has been reached.

    This is a tunable parameter and can be modified to meet your business requirements.

  • A file is modified either through SMB or NFS access.

  • A file for which there are computed hashes is restored using the snap restore command.

  • A volume that contains SMB shares that are BranchCache-enabled is restored using the snap restore command.