Designing High Availability Solutions with HP Serviceguard and HP Integrity Virtual Machines

14
Figure 9: Serviceguard multi-cluster consolidation using VM guests
Storage considerations
An important distinction between VM as Serviceguard package and VM as Serviceguard node configurations is that
VM as Serviceguard node configurations only support whole disk VM backing stores. One reason for this restriction is
that it is not possible to set timeouts on logical volumes or file systems presented as backing stores to the VM guest.
Also, any errors generated from these types of backing stores are not passed through the virtualization layers from the
VM host to VM guest that allows the Serviceguard running in the VM to react to these conditions. Another reason
relates to disk I/O performance and the speed at which I/O requests can be completed prior to a VM node failure,
which can affect cluster reformation time (see the usage considerations section for more information on handling
outstanding I/O requests during a VM node failure).
As for data used by applications protected by Serviceguard packages, it must reside on shared storage that is
physically connected to all nodes that can run the package and can be placed in LVM or SLVM logical volumes,
VxVM disk groups, on a cluster file system (CFS), or on a shared NFS file system. The storage for the application data
presented to the VM guest by the VM host must be whole disks so the logical volume and file system structures on this
storage can be accessed by the other nodes in the cluster during a Serviceguard package failover.
Figure 10a: HP-UX VM as Serviceguard node storage configuration
Before consolidation After consolidation
VM Host VM Host
VM Guest 2
VM Guest 2
VM Guest 1
Failover
VM Guest 1
Failover
SG Cluster
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
Before consolidation After consolidation
VM Host VM Host
VM Guest 2
VM Guest 2
VM Guest 1
Failover
VM Guest 1
Failover
SG Cluster
SG Cluster
VM Host VM Host
VM Guest 2
VM Guest 2
VM Guest 1
Failover
VM Guest 1
Failover
SG Cluster
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
Physical Node
Physical Node
Failover
SG Cluster
VM Host
Physical Node
VM
Backing
Store
Application
Data
Whole Disk Volume Group or CFS
VM Guest
Failover
Serviceguard Cluster
VM Host
Physical Node
VM
Backing
Store
Application
Data
Whole Disk Volume Group or CFS
VM Guest
Failover
Serviceguard Cluster