PRIMECLUSTER Global Disk Services Configuration and Administration Guide 4.1 (Linux)

A.2.11 Online Volume Expansion

• Volume Configuration Limitations

  Online volume expansion is available for volumes in the following configurations.

  • Single volume
  • Mirror volume
    • Any mirroring multiplicity is supported.
    • Hierarchized groups are supported.
      

   

• Online Mirror Volume Expansion

  For mirror volumes with mirroring multiplicity of two and higher, change the mirroring multiplicity to one, expand the volumes, and then execute synchronization copying for re-mirroring. See the outline of the operating procedures below. These operations are executable without stopping applications using the volumes.

  1. Disconnect disks and lower level groups from the mirror group to change the mirroring multiplicity to one.
  2. Expand the volume size with the sdxvolume -S command.
  3. Reconnect the disks and lower level groups disconnected in step 1) with the mirror group.

  If the mirror volumes are active, resynchronization copying is automatically performed after step 3) is done. If the mirror volumes are inactive, similar copying is automatically performed when they are started.
  

   

• Stripe Type Volume and Concatenation Type Volume Expansion

  The capacity of stripe type volumes and concatenation type volumes cannot be expanded. To expand one of these types, back up data, recreate the volume, and then restore the data back to the volume. In configurations where a striping group or a concatenation group is connected to a mirror group (with any multiplicity), volume expansion applied using the striping or concatenation feature is possible.

  
  For the methods of backing up and restoring, see "Backing Up and Restoring."
  

   

• Concatenation and Online Volume Expansion

  Even if there is no sufficient continuous free space after the last block of a volume, by concatenating unused disks, online volume expansion will be available. Online volume expansion is available for volumes that meet all of the following conditions:

  • Volumes belong to a mirror group;
  • To the mirror group, one or more concatenation groups are connected;
  • To each of the concatenation groups, one or more disks are connected.

  To use this function, create volumes in configuration conforming to these conditions in advance. For example, if there is only one available disk, connect only the disk to a concatenation group, connect the concatenation group to a mirror group, and create volumes in the mirror group.

   

• Expansion of Areas Used by Applications

  After volumes are expanded, applications such as file systems and databases need to recognize the expanded areas with methods specific to the applications.
  If an application using a volume cannot recognize an expanded volume area, do not expand the volume. If such a volume is expanded, the application may no longer operate normally or volume data may be unavailable. A volume that contains the GFS Shared File System cannot be expanded.