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Creating and managing linked break-off snapshot volumes

Break-off snapshots are suitable for write-intensive volumes, such as database redo logs.

For linked break-off snapshots, you must prepare a volume that is to be used as the snapshot volume. This must be the same size as the volume for which the snapshot is being created, and it must also have the same region size.

See "Creating a volume for use as a full-sized instant or linked break-off snapshot" on page 305.

The attributes for a snapshot are specified as a tuple to the vxsnap make command. This command accepts multiple tuples. One tuple is required for each snapshot that is being created. Each element of a tuple is separated from the next by a slash character (/). Tuples are separated by white space.

 To create and manage a linked break-off snapshot

  1. Use the following command to link the prepared snapshot volume, snapvol, to the data volume:

    # vxsnap [-g diskgroup] [-b] addmir volume mirvol=snapvol \


    The optional mirdg attribute can be used to specify the snapshot volume's current disk group, snapdg. The -b option can be used to perform the synchronization in the background. If the -b option is not specified, the command does not return until the link becomes ACTIVE.

    For example, the following command links the prepared volume, prepsnap, in the disk group, mysnapdg, to the volume, vol1, in the disk group, mydg:

    # vxsnap -g mydg -b addmir vol1 mirvol=prepsnap \


    If the -b option is specified, you can use the vxsnap snapwait command to wait for the synchronization of the linked snapshot volume to complete, as shown in this example:

    # vxsnap -g mydg snapwait vol1 mirvol=prepsnap \


  2. To create a linked break-off snapshot, use the following form of the vxsnap make command.

    # vxsnap [-g diskgroup] make source=volume/snapvol=snapvol\


The snapdg attribute must be used to specify the snapshot volume's disk group if this is different from that of the data volume.

For example, to use the prepared volume, prepsnap, as the snapshot for the volume, vol1, in the disk group, mydg, use the following command:

# vxsnap -g mydg make \


  1. Use fsck (or some utility appropriate for the application running on the volume) to clean the temporary volume's contents. For example, you can use this command with a VxFS file system:

    # fsck -V vxfs /dev/vx/dsk/diskgroup/snapshot

The specified device must have a valid entry in the /etc/filesystems file.

  1. If you require a backup of the data in the snapshot, use an appropriate utility or operating system command to copy the contents of the snapshot to tape, or to some other backup medium.
  2. You now have the following choices of what to do with a linked break-off snapshot: