HP XC System Software Installation Guide Version 4.0

Table 1-2 Role and Service Placement for Improved Availability (continued)
Special Considerations for Role Assignment
Service is Delivered in This
RoleService Name
The kdump service enables you to save and access stored crash
dumps if the HP XC head node becomes unavailable.
The kdump service is present on the head node by default and
cannot be moved. Thus, to achieve improved availability of
the kdump service you must assign the
avail_node_management role the other node in the
availability set with the head node.
Using Serviceguard to enable improved availability of the
kdump service requires shared fiber channel storage connecting
the head node and the other node in the availability set. The
shared storage must contain an LVM volume that includes an
ext3 file system type for the dump partition to be mounted
locally on one of the nodes and served to the rest of the nodes
in the HP XC configuration.
For more information about creating an LVM volume, see
Section 3.6.3 (page 61).
This configuration enables Serviceguard to relocate the kdump
service to the second node in the availability set if the HP XC
head node becomes unavailable.
Dependency on Other Services: None.
avail_node_managementCrash dump (kdump)
The login role supplies the LVS director service. LVS requires
the login role on three nodes to attain improved availability:
• One node which is always a real server
• A pair of nodes to act as the LVS director and a backup for
the LVS director associated into an availability set. The LVS
director also acts as a real server; the backup never does.
This means that to have n real servers during normal operation,
you assign the login role to n+1 nodes because the backup for
the LVS director is never a real server, but it must have a
login role to act as a backup. When failover occurs, the
backup takes over the director role, but it does not become a
real server. This means that when the LVS director service is
failed over, there is one less real server available (temporarily)
because the director, which was a real server, is unavailable.
login
Linux Virtual Server
(LVS) director
Within the availability set, the higher numbered node is the
LVS director, and the lower numbered node is the backup for
the LVS director.
Thus, to achieve improved availability of the LVS director
service, you must assign at least three nodes with the login
role:
• Assign the login to the first node in the availability set.
• Assign the login role to the second node in the availability
set.
• Assign the login role to any other node in the system. This
node acts as a real server.
The nodes you associate into the availability set must have an
external Ethernet connection configured as well.
Dependency on Other Services: To function properly, the
LVS director service requires a highly available dbserver
service.
For more information about the login role, see Section F.3.10
(page 219).
32 Preparing for a New Installation