SVS200 (T1714-96008, June 2006)

130 Overview of Volume Manager and Custom Volume Size

host’s host mode is 2C (Windows Extension). If the host mode is not 2C, change the host mode to 2C

before performing the Volume Manager operation.

Overview of Custom Volume Size

This section describes the Custom Volume Size (CVS) function, configuring CVS, and requirements of the

storage subsystem ID (SSID). CVS operations include:

• ”Viewing concatenated parity groups” on page 180

• ”Converting logical volumes to space” on page 180

• ”Creating CVS volumes (Install CV operation)” on page 181

• ”Deleting CVS volumes” on page 183

• ”Converting CVs back to FVs (Volume Initialize operation)” on page 183

• ”Re-creating CVs after initializing the VDEV (Make Volume operation)” on page 185

CVS function

CVS works on each VDEV that consists of a group of logical volumes (LDEVs or LUs) in a parity group.

Usually, one VDEV consists of some fixed volumes (FV) and some free space. The emulation type

determines the number of fixed volumes. A CVS volume usually consists of at least one fixed volume (FV),

one or more customized volumes (CVs), and some free space. CVS allows you to configure variable-size

volumes, which are usually smaller than normal (fixed-size) volumes. Therefore, if several frequently

accessed files are located in the same logical volume, use CVS to reduce conflicts by splitting the logical

volumes and scattering the files, although there are some instances where access is delayed while a file is

being accessed. This can improve data accessing performance. CVS can also divide a logical volume

into smaller ones for a command device, which efficiently exploits the disk’s capacity.

CVS operations include: Volume to Space, Install CV, Volume Initialize, and Make Volume. The Volume to

Space function formats one or more LDEVs on a selected Virtual Device (VDEV) into free space. That free

space can either be used to install one or more variable-sized volumes (CVs) using the Install CV function,

or left as free space for future use. The Volume Initialize function de-installs all variable sized volumes

(CVs) under a CVS volume, and reformats the CVS volume as a normal volume (VDEV). The Make Volume

function clears all variable-sized volumes (CVs) under a CVS volume and creates an initial volume (VDEV)

consisting of the new user-defined CVs.

For an overview of how the Volume Initialize function works, see Figure 79. For an overview of how the

Make Volume function works, see Figure 80.

Figure 79 Overview of Volume Initialize function