HP Veritas Volume Manager 5.0 -UX 11i v3 Private and public disk regions, simple, nopriv, command, smallest, public region, private region, ” on page 205), Splitting disk groups

80Administering disks

Disk devices

Private and public disk regionsMost VM disks have two regions:

private region A small area where configuration information is stored. A disk header label, configuration records for VxVM objects (such as volumes, plexes and subdisks), and an intent log for the configuration database are stored here. The default private region size is 32 megabytes (except for VxVM boot disk groups where the private region size must be 1 megabyte), which is large enough to record the details of several thousand VxVM objects in a disk group.

Under most circumstances, the default private region size should be sufficient. For administrative purposes, it is usually much simpler to create more disk groups that contain fewer volumes, or to split large disk groups into several smaller ones (as described in “Splitting disk groups” on page 205). If required, the value for the private region size may be overridden when you add or replace a disk using the vxdiskadm command.

Each disk that has a private region holds an entire copy of the configuration database for the disk group. The size of the configuration database for a disk group is limited by the size of the smallest copy of the configuration database on any of its member disks.

public region An area that covers the remainder of the disk, and which is used for the allocation of storage space to subdisks.

A disk’s type identifies how VxVM accesses a disk, and how it manages the disk’s private and public regions. The following disk access types are used by VxVM:

simple	The public and private regions are on the same disk area (with
	the public area following the private area).
nopriv	There is no private region (only a public region for allocating
	subdisks). This is the simplest disk type consisting only of
	space for allocating subdisks. Such disks are most useful for
	defining special devices (such as RAM disks, if supported) on
	which private region data would not persist between reboots.
	They can also be used to encapsulate disks where there is
	insufficient room for a private region. The disks cannot store
	configuration and log copies, and they do not support the use
	of the vxdisk addregion command to define reserved regions.
	VxVM cannot track the movement of nopriv disks on a SCSI
	chain or between controllers.