Mirror Pools

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Mirror pools make it possible to divide the physical volumes of a volume group into separate pools.

A mirror pool is made up of one or more physical volumes. Each physical volume can only belong to one mirror pool at a time. When creating a logical volume, each copy of the logical volume being created can be assigned to a mirror pool. Logical volume copies that are assigned to a mirror pool will only allocate partitions from the physical volumes in that mirror pool. This provides the ability to restrict the disks that a logical volume copy can use. Without mirror pools, the only way to restrict which physical volume is used for allocation when creating or extending a logical volume is to use a map file. Thus, using mirror pools greatly simplify this process. Mirror pools can be created with the extendvg command or the chpv command.

You must specify a mirror pool name when you create a new mirror pool. Mirror pool names must conform to the following rules:
  • Can only contain alphanumeric characters or the _ (underscore), - (minus sign), or . (period) characters.
  • Must be less than or equal to 15 characters.
  • Must be unique in the volume group.

Once mirror pools have been used in a volume group, the volume group can no longer be imported into a version of AIX that does not support mirror pools. This includes any version of AIX before 6.1.1.0. Additionally, in order to use mirror pools with enhanced concurrent-mode LVM, all nodes in the cluster must support mirror pools.

Mirror pool strictness

Mirror pool strictness can be used to enforce tighter restrictions on mirror pool use. Mirror pool strictness can have one of the following three values:

off
When mirror pool strictness is set to off, no restrictions are placed on mirror pool use. This is the default value.
on
When mirror pool strictness is set to on, each logical volume copy created in the volume group must be assigned to a mirror pool.
super
When mirror pool strictness is set to super, the following restrictions apply:
  • Local and remote physical volumes cannot belong to the same mirror pool.
    Note: For more information on local and remote physical volumes, refer to the HACMP/XD GLVM documentation.
  • There can be a maximum of three mirror pools in a volume group.
  • Each mirror pool must contain at least one copy of each logical volume in the volume group.