2.5.1.2 Solstice DiskSuite Mirroring Alternatives

Consider the following alternatives when deciding whether to mirror root (/) file systems under Solstice DiskSuite. The issues mentioned in this section are not applicable to Sun StorEdge Volume Manager or Cluster Volume Manager configurations.

• For highest availability, mirror root on a separate controller with metadevice state database replicas on three different controllers. This tolerates both disk and controller failures.

• Under Solstice DiskSuite, to tolerate disk media failures only:

  • Mirror the root disk on a second controller and keep a copy of the metadevice state database on a third disk on one of the controllers.

    or

  • Mirror the root disk on the same controller and keep a copy of the metadevice state database on a third disk on the same controller.

  It is possible to reboot the system before performing maintenance in these configurations, because a quorum is maintained after a disk media failure. These configurations do not tolerate controller failures, with the exception that option `a' tolerates controller failure of the controller that contains metadevice state database replicas on a single disk.

  If the controller that contains replicas on two disks fails, quorum is lost.

• Mirroring the root disk on the same controller and storing metadevice state database replicas on both disks tolerates a disk media failure and prevents an immediate takeover. However, you cannot reboot the machine until after maintenance is performed because more than half of the metadevice state database replicas are not available after the failure.

• Do not mirror the root disk, but perform a daily manual backup of the root disk (with dd(1) or some other utility) to a second disk which can be used for booting if the root disk fails. Configure the second disk as an alternate boot device in the OpenBoot PROM. The /etc/vfstab file might need to be updated after the dd(1) operation to reflect the different root partition. Configure additional metadevice state database replicas on Slice 4 of the second disk. In the event of failure of the first disk, these will continue to point to the multihost disk replicas. Do not copy and restore the metadevice state database. Rather, let Solstice DiskSuite do the replication.