Most VM disks consist of the following regions:
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, 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.
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.
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:
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
The public and private regions are both configured on a single extended partition, such as partition 5, with the public area following the private area. The partition number (displayed as
Auto-configured disks (with disk access type
auto) support the following disk formats:
The disk is formatted as a Cross-platform Data Sharing (CDS) disk that is suitable for moving between different operating systems. This is the default format for disks that are not used to boot the system.Typically, most disks on a system are configured as this disk type. However, it is not a suitable format for boot, root or swap disks, for mirrors or hot-relocation spares of such disks, or for Extensible Firmware Interface (EFI) disks. Also note that partition 3 is used for both the private and public regions of a CDS disk.
vxcdsconvert utility can be used to convert disks to the
vxcdsconvert(1M) manual page.
fdiskto create a partition table on a CDS disk, this erases the CDS information and could cause data corruption.
By default, auto-configured non-EFI disks (for example, disks with an MS-DOS or Sun label, or without a disk label) are formatted as
cdsdisk disks when they are initialized for use with VxVM. You can change the default format by using the
vxdiskadm command to update the
/etc/default/vxdisk defaults file
See "Displaying or changing default disk layout attributes" on page 96.
vxdisk(1M) manual page.
Auto-configured EFI disks are formatted as
sliced disks by default.