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Enabling FastResync on a volume

The recommended method for enabling FastResync on a volume with a version 20 DCO is to use the vxsnap prepare command.

See "Preparing a volume for DRL and instant snapshots" on page 260.

  Note   You need a FastResync license to use this feature.

FastResync performs quick and efficient resynchronization of stale mirrors. It also increases the efficiency of the VxVM snapshot mechanism when used with operations such as backup and decision support.

See "Administering volume snapshots" on page 287.

See "FastResync" on page 65.

There are two possible versions of FastResync that can be enabled on a volume:

• Persistent FastResync holds copies of the FastResync maps on disk. These can be used for the speedy recovery of mirrored volumes if a system is rebooted. This form of FastResync requires that either a version 0 or a version 20 data change object (DCO) and DCO volume first be associated with the volume.

  See "Adding a version 0 DCO and DCO volume" on page 337.

  See "Upgrading existing volumes to use version 20 DCOs" on page 264.

  See "Preparing a volume for DRL and instant snapshots" on page 260.

• Non-Persistent FastResync holds the FastResync maps in memory. These do not survive on a system that is rebooted.

By default, FastResync is not enabled on newly created volumes. Specify the fastresync=on attribute to the vxassist make command if you want to enable FastResync on a volume that you are creating.

  Note   It is not possible to configure both Persistent and Non-Persistent FastResync on a volume. Persistent FastResync is used if a DCO is associated with the volume. Otherwise, Non-Persistent FastResync is used.

To turn FastResync on for an existing volume, specify fastresync=on to the vxvol command as shown here:

# vxvol [-g diskgroup] set fastresync=on volume

To use FastResync with a snapshot, FastResync must be enabled before the snapshot is taken, and must remain enabled until after the snapback is completed.