Managing Serviceguard A.11.20, March 2013

Redundant Disk Storage
Each node in a cluster has its own root disk, but each node is also physically connected to several
other disks in such a way that more than one node can obtain access to the data and programs
associated with a package it is configured for. This access is provided by a Storage Manager,
such as Logical Volume Manager (LVM), or Veritas Volume Manager (VxVM) (or Veritas Cluster
Volume Manager (CVM). LVM and VxVM disk storage groups can be activated by no more than
one node at a time, but when a failover package is moved, the storage group can be activated
by the adoptive node. All of the disks in the storage group owned by a failover package must be
connected to the original node and to all possible adoptive nodes for that package. Disk storage
is made redundant by using RAID or software mirroring.
Supported Disk Interfaces
The following interfaces are supported by Serviceguard for disks that are connected to two or more
nodes (shared data disks):
• Single-ended SCSI
• SCSI
• Fibre Channel
• iSCSI
Not all SCSI disks are supported. See the HP Unix Servers Configuration Guide (available through
your HP representative) for a list of currently supported disks.
NOTE: In a cluster that contains systems with PCI SCSI adapters, you cannot attach both PCI and
NIO SCSI adapters to the same shared SCSI bus.
External shared Fast/Wide SCSI buses must be equipped with in-line terminators for disks on a
shared bus. Refer to the “Troubleshooting” chapter for additional information.
When planning and assigning SCSI bus priority, remember that one node can dominate a bus
shared by multiple nodes, depending on what SCSI addresses are assigned to the controller for
each node on the shared bus. All SCSI addresses, including the addresses of all interface cards,
must be unique for all devices on a shared bus.
Using iSCSI LUNs as Shared Storage
This following guidelines are applicable when iSCSI LUNs are used as a shared storage:
• iSCSI storage can be configured on an Automatic Port Aggregation (APA) (page 78) LAN
interface.
• iSCSI storage is supported with software initiator models. For information on configuring iSCSI
disks, see HP-UX iSCSI Software Initiator Support Guide available at http://www.hp.com/
go/hpux-networking-docs -> HP-UX iSCSI (SCSI Over TCP/IP) Software.
• Configuring multiple paths from different networks to the iSCSI LUN is not supported.
• iSCSI storage configured over LAN is similar to any other LANs that are part of the cluster.
• iSCSI storage devices with Persistent Reservations are supported on only LVM volume groups
and vxfs filesystem, and not on VxVM or CVM volume groups.
• iSCSI storage devices are supported with only IPv4 networks.
32 Understanding Serviceguard Hardware Configurations