SMB limitations

This topic describes the limitations of IBM Spectrum Scale SMB protocol.

IBM Spectrum Scale allows concurrent access to the same data file through SMB and NFS, and through native POSIX access.

For more information on SMB client access and limitations, see Multiprotocol export considerations.

SMB server limitations

The SMB server does not indicate mount points to the SMB client. This can have the effect that SMB clients query free space in the wrong directory, if different filesets are linked to subfolders in an SMB share. When an SMB CREATE request for creating or replacing a file fails, an empty file can be left behind.

SMB share limitations

Consider all the limitations and support restrictions before you create an SMB share.

SMB share limitations include the following:
  • NTFS alternate data streams are not supported. For example, named streams generated by a Mac OS X operating system cannot be stored directly.

    Enabling vfs_fruit will partially lift this limitation. For more information, see Support of vfs_fruit for the SMB protocol

  • The encryption status of files cannot be queried or changed from SMB clients. Use the CLI commands instead.
  • When propagation of opportunistic locks across protocols is enabled (SMB option gpfs:leases), then Level 2 oplocks are not granted and Exclusive or batch oplocks are not broken down to Level 2 oplocks and are revoked from the system.
  • Concurrent access to the same files or directories from many SMB connections on multiple nodes can result in scalability problems.
  • Symbolic links cannot be created or changed from SMB clients and are not reported as symbolic links.
  • Symbolic links created via NFS or directly in the file system will be respected as long as they point to a target under the same shared directory.
  • Windows Internet Name Service (WINS) is not supported.
  • Retrieving Quota information using NT_TRANSACT_QUERY_QUOTA is not supported.
  • Setting Quota information using NT_TRANSACT_SET_QUOTA is not supported.
  • Setting the maximum number of connections to a share is not supported. The MMC GUI allows specifying this parameter, but it cannot be set on an IBM Spectrum Scale cluster.
  • UNIX Extensions are not supported.
  • You cannot create a shadow copy of a shared folder using a remote procedure call from a shadow copy client. Backup utilities, such as Microsoft Volume Shadow Copy Service, cannot create a shadow copy of a shared folder using a procedure call.
  • The Branch Cache hash operations using SRV_READ_HASH IOCTL are not supported.
  • Leases are not supported.
  • Only the SMB2 and SMB3 protocol versions are supported.
  • No support of dynamic ACLs and SACLs.
  • SMB Direct (SMB over RDMA) is not supported.
  • Multi-channel for SMB is not supported.
  • Durable handles are not supported.
  • Resilient® handles are not supported.
  • Persistent handles are not supported.
  • Storing arbitrary data in Security Descriptors is not supported.
  • Pre-allocating space larger than the file size is not supported. A check for the available disk space is used instead when processing an allocation request from an SMB client.
  • The Witness notification protocol is not supported.
  • Continuous Availability (CA) SMB exports are not supported.
  • Scaleout SMB exports are not supported.
  • Creating snapshots from an SMB client is not supported.
  • Application instance ID is not supported.
  • FSCTL_SET_ZERO_DATA is only supported on sparse files.
  • Setting compression from an SMB client or querying the compression state from an SMB client is not supported.
  • All CES nodes need to be the same hardware architecture (x86 versus Power®) and the same endianness (little endian versus big endian).
  • Rolling code upgrade is not supported for SMB. The SMB service needs to be stopped on all CES nodes for the upgrade to ensure that the same SMB software level is used on all CES nodes.
  • Start of changeWhen upgrading IBM Spectrum Scale from version 4.2.3.19 to version 5.0.5, the max protocol level for SMB support does not automatically change to the latest. This has to be done manually.End of change
  • The AAPL create context used by Mac OS clients is not supported. When enabling VFS fruit AAPL create contexts are supported.
  • The number of open files for each SMB connection is limited to 16384.
  • IBM Spectrum Scale can host a maximum of 1,000 SMB shares. There must be less than 3,000 SMB connections per protocol node and less than 20,000 SMB connections across all protocol nodes.
  • No support of SID history.
  • The SMB service requires file names and directory names to use the UTF-8 encoding. Files and directories with different encoding cannot be accessed through the SMB protocol.
  • The NFSv4 SYNCHRONIZE bit is no longer automatically set on file ACLs. Windows clients expect SYNCHRONIZE on ACLs to correctly allow rename.
  • 8.3 short name creation is not supported
  • IBM Spectrum Scale can act as a MS-DFS target or can redirect an entire share. But it does not allow any redirects from within an exported tree.

SMB node limitations

IBM Spectrum Scale allows a maximum of 16 SMB server nodes in a CES cluster.

SMB encryption on Power systems

SMB encryption on Power systems requires Openssl 1.0.2 or newer for crypto-hardware acceleration, which is provided by RHEL 7.4 or newer. Also, the hardware crypto-acceleration is only available on POWER8® or newer systems.