Managing Serviceguard 12th Edition, March 2006

Understanding Serviceguard Hardware Configurations
Redundant Disk Storage
Chapter 246
Disk Arrays using RAID Levels and Multiple Data Paths
An alternate method of achieving protection for your data is to employ a
disk array with hardware RAID levels that provide data redundancy,
such as RAID Level 1 or RAID Level 5. The array provides data
redundancy for the disks. This protection needs to be combined with the
use of redundant host bus interfaces (SCSI or Fibre Channel) between
each node and the array.
The use of redundant interfaces, configured with LVM’s PV Links
feature or VxVM’s dynamic multipathing (DMP), protects against single
points of failure in the I/O channel, and RAID 1 or 5 configuration
provides redundancy for the storage media. (PV links are also known as
alternate links in LVM, or multiple paths in VxVM.)
DMP is included in all of the Serviceguard Storage Managment Suite
bundles. It is also available as a separate component of VxVM. DMP for
active/active devices requires B9116AA ( VxVM 3.5) or B9116BA (VxVM
4.1), but DMP for active/passive devices is available for no charge with
the base product, Base-VxVM.
Monitoring of Disks Through Event Monitoring
Service
If you are using LVM, you can configure disk monitoring to detect a
failed mechanism by using the disk monitor capabilities of the EMS HA
Monitors, available as a separate product (B5736DA). Monitoring can be
set up to trigger a package failover or to report disk failure events to a
Serviceguard, to another application, or by email. For more information,
refer to the manual Using High Availability Monitors (B5736-90042),
available at http://docs.hp.com -> High Availability.
Replacement of Failed Disk Mechanisms
Mirroring provides data protection, but after a disk failure, the failed
disk must be replaced. With conventional disks, this is done by bringing
down the cluster and replacing the mechanism. With disk arrays and
with special HA disk enclosures, it is possible to replace a disk while the
cluster stays up and the application remains online. The process is
described under “Replacing Disks” in the chapter “Troubleshooting Your
Cluster.”