AFM optimized recovery version v2

During the recovery event triggered on the AFM fileset, AFM determines all the operations that are pending and yet to synchronize with home. If rename and remove operations, AFM requires to read the home data.

If the AFM fileset contains large volume of data, recovery might take time to identify operations that are yet to synchronize and in pending state. To overcome this delay, AFM optimized recovery version v2 that can be enabled on the AFM fileset Single-Writer mode or AFM-DR primary mode fileset.

After the AFM optimized recovery version v2 is enabled, AFM avoids reading home directory, and uses GPFS policy to run at the home. This step helps in finding the relevant information to quickly identify the list of rename and recovery operations that needs to be synchronized and then queue them to the Gateway Node.

To run policy at home, AFM target must be running IBM Storage Scale GPFS filesystem. You can apply optimized AFM recovery version v2 on AFM Single-Writer and AFM-DR primary mode fileset only.

If newer AFM recovery version v2 observes any failure, AFM automatically uses the older version v1 and try to complete the operation.

The AFM recovery version v2 can be enabled on the AFM Single-Writer or AFM-DR primary fileset. You can enable AFM recovery version v2 either at the time of fileset creation by using mmcrfileset command or by changing existing fileset by using mmcrfileset command.

Before you enable the AFM recovery version v2 on the existing fileset, the IBM Storage Scale cluster version and file system version must be upgraded to the latest release level.

Note: The afmRecoveryVer2 parameter cannot be set on AFM Single Write mode or AFM DR primary mode fileset while running GPFS or NSD backend targets. This parameter is only supported on AFM fileset using NFS backend/target.

Example

  1. To create an AFM fileset and enable recovery v2 on it, issue the following command:
    mmcrfileset fs1 afmSW-recv2 -p afmMode=sw,afmTarget=home:/gpfs/fs1/target1,afmRecoveryVer2=yes --inode-space newer
  2. To update an existing AFM SW mode fileset and enable recovery v2 on it, AFM fileset must be stopped or unlinked. After the parameter is set, fileset can be started or unlinked.
    mmafmctl fs1 stop -j afmSW-recv1
    mmchfileset fs1 afmSW-recv1 -p afmRecoveryVer2=yes
    mmafmctl fs1 start -j afmSW-recv1
    For more information, see File system format changes between versions of IBM Spectrum Scale.
  3. In IBM Storage Scale 5.1.6, new file systems are created at file system format level 29.00. To update a file system from an earlier format to format level 29.00, issue the following command: 
    mmchfs Device -V full
    Where,

    Device is the device name of the file system.

  4. The Enable AFM recovery version v2 feature of the IBM Storage Scale 5.1.6 requires a file system to be at format number 29.00 or later.