A layered volume is a virtual Veritas Volume Manager object that is built on top of other volumes. The layered volume structure tolerates failure better and has greater redundancy than the standard volume structure. For example, in a striped-mirror layered volume, each mirror (plex) covers a smaller area of storage space, so recovery is quicker than with a standard mirrored volume.
Example of a striped-mirror layered volume shows a typical striped-mirror layered volume where each column is represented by a subdisk that is built from an underlying mirrored volume.
Example of a striped-mirror layered volume
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The volume and striped plex in the "Managed by User" area allow you to perform normal tasks in VxVM. User tasks can be performed only on the top-level volume of a layered volume.
Underlying volumes in the "Managed by VxVM" area are used exclusively by VxVM and are not designed for user manipulation. You cannot detach a layered volume or perform any other operation on the underlying volumes by manipulating the internal structure. You can perform all necessary operations in the "Managed by User" area that includes the top-level volume and striped plex (for example, resizing the volume, changing the column width, or adding a column).
System administrators can manipulate the layered volume structure for troubleshooting or other operations (for example, to place data on specific disks). Layered volumes are used by VxVM to perform the following tasks and operations: