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VxVM can place various files from the root file system, swap device, and other file systems on the root disk under VxVM control. This is called rootability. The root disk (that is, the disk containing the root file system) can be put under VxVM control through the process of encapsulation.
The root disk can be encapsulated using the vxdiskadm command as described in Encapsulating a disk. Once encapsulated, the root disk can also be mirrored by using the vxdiskadm. command as described in Mirroring an encapsulated root disk.
Encapsulation converts existing partitions on that disk to volumes. Once under VxVM control, the root and swap devices appear as volumes and provide the same characteristics as other VxVM volumes. A volume that is configured for use as a swap area is referred to as a swap volume, and a volume that contains the root file system is referred to as a root volume.
It is possible to mirror the rootvol, and swapvol volumes, as well as other parts of the root disk that are required for a successful boot of the system (for example, /usr). This provides complete redundancy and recovery capability in the event of disk failure. Without VxVM rootability, the loss of the root, swap, or usr partition prevents the system from being booted from surviving disks.
Mirroring disk drives that are critical to booting ensures that no single disk failure renders the system unusable. A suggested configuration is to mirror the critical disk onto another available disk (using the vxdiskadm command). If the disk containing root and swap partitions fails, the system can be rebooted from a disk containing mirrors of these partitions.
Suggested rootability configuration shows one possible assignment of disks in the bootdg disk group.
Suggested rootability configuration
Click the thumbnail above to view full-sized image.
This arrangement consists of the encapsulated root disk, the root disk mirror, and at least one spare disk. If hot-relocation is enabled and either the root disk or its mirror fails during use, VxVM automatically recreates the failed plexes on the spare disk by copying from the plexes on remaining disk. If the spare disk is suitable, it may then be configured to be booted from, or you can use it to recover the contents of the failed disk when it is replaced.
Note
Disks with the cdsdisk format cannot be used as hot-relocation spares or root disk mirrors. Hot-relocation spares or root disk mirrors must be configured with the sliced format.
Recovering a system after the failure of an encapsulated root disk requires the application of special procedures.
See the Veritas Volume Manager Troubleshooting Guide.