AFM and AFM DR limitations

The common limitations for both AFM and AFM DR functions include:
  • The following table shows the OS and architecture support matrix and supported AFM function:
    Table 1. Supported function and supported OS/architecture
    OS and architecture Fileset Node roles Comments
    Linux® on Power® and x86
    SW/IW/RO/LU
    primary/secondary
    Gateway
    Application
    Manager
    		  
    Linux on Z
    SW/IW/RO/LU
    primary/secondary
    Gateway
    Application
    Manager
    		  
    AIX® on Power
    SW/IW/RO/LU
    primary
    Gateway
    Application
    		 AIX cannot be an AFM home site or an AFM-DR secondary site.
  • An AFM home site that is not an IBM Storage Scale cluster:
    • An AFM cache site can be configured to connect with any home site that provides access to the home data through the NFSv3 protocol. The home site is not required to be an IBM Storage Scale cluster.
    • In this scenario, the mmafmconfig command cannot not be issued on the AFM home site. Therefore, the AFM cache site cannot cache or update extended attributes (EAs), access control lists (ACLs), file spareness, or AFM psnaps.
    • The IBM Storage Scale support team helps customers to investigate problems in this scenario but only to address issues with the AFM cache site that runs IBM Storage Scale. Any problems at the AFM home site, or its file system, must be addressed by the customer.
    • For AFM-DR configurations, both the primary and secondary sites must be IBM Storage Scale clusters.
  • An AFM home site that runs IBM Storage Scale on AIX:
    • The mmafmconfig command is not supported on AIX. Therefore, the AFM cache site cannot cache or update extended attributes (EAs), access control lists (ACLs), file spareness, or AFM psnaps.
    • AFM does not support AIX nodes as an exporter of NFS. That is, AFM does not support NFS mounting exports that are reached through a system that runs on AIX.
    • Because of the previous limitations, AIX nodes cannot act as an AFM home site or as an AFM-DR secondary site.
    • AIX is not supported as a gateway node for AFM fileset modes.
    • AIX is not supported as an AFM home site or AFM-DR secondary site.
  • The mmclone command is not supported on AFM cache and AFM DR primary filesets. Clones that are created at home for AFM filesets are treated as separate files in the cache.
  • Quality of service is not tested on AFM and AFM Async DR filesets.
  • Connecting an AFM-DR fileset to IBM Storage Protect for Space Management use case is not supported.
  • The NSD protocol for communication does not support AFM and AFM DR filesets on Linux on Z.
  • Connecting AFM DR fileset to IBM Spectrum Archive is not supported.
  • AFM and Async DR is not supported on clusters that have Windows nodes.
  • Cascading relationships with AFM caches and AFM primary filesets are not tested.
  • Fileset snapshot restore is not supported for AFM and AFM DR filesets.
  • Files in an AFM or AFM DR fileset, which are shared by using SMB, an error message E_ACCESS might appear if SMB holds locks on the files. When the locks are released by SMB, AFM replicates again and processes the files from the AFM or AFM DR fileset.
  • The dm_write_invis() function is not supported on AFM and AFM DR filesets.
  • The dm_read_invis() function is not supported on AFM and AFM DR filesets, if a file is not cached.
  • The File Audit logging feature is not supported on AFM or AFM DR filesets.
  • Immutability and appendOnly features are not supported on AFM filesets.
  • AFM and AFM DR filesets do not replicate security, system, or trusted extended attributes.
  • The --iam-mode option is not supported on AFM filesets.
  • AFM and AFM DR do not support DM Punch Hole method (GPFS API 'dm_punch_hole').
  • To enable the Kerberos security for an AFM-DR fileset, the AFM-DR secondary must be given the read/write access.
  • If a file is evicted from an AFM fileset, the snapshot file of the evicted file contains zeros.
  • Eviction is not supported on an AFM-DR primary fileset and an AFM-DR secondary fileset.
  • The following file attributes are maintained locally in the cache but these are not replicated:
    • Control attributes
    • Direct I/O
    • Replication factors
    • Fileset quotas
    • Storage pool flags
    • Special file types such as FIFO, socket, block, character device
  • Hard links can be created on the cache. Hard links on the home are displayed as individual files in the cache during the lookup. To prefetch hard links from home, run the --metadata-only option as the first operation.
  • File locking across the cache and the home is not supported.
  • User extended attributes, ACLs, and sparse files supported only on the home where the mmafmconfig command is run.
  • Parallel data transfer is supported only in Linux-only clusters. If a home is a mix of architectures (x86 and ppc), parallel data transfer works only for the set of nodes that belong to any one architecture, depending on which architecture serves the data transfer first.
  • If encryption is configured on a home site that is running on a file system, which AFM uses as a GPFS backend target (multi-cluster remote mount), of an IBM Storage Scale cluster, ensure that the cache cluster is also configured the same way as the home cluster. Because of this configuration, AFM can access the files on the target file system for the replication.
  • Start of changeOnline replication of a dependent fileset is not supported on an AFM DR fileset with a GPFS/multi cluster backend.End of change