HP XC System Software Installation Guide Version 3.1

In this release, improved availability is supported for the services listed in Table 1-2. Also listed in the
table are things to consider about the role assignments if you plan to implement improved availability for
one or more of these services.
Read Appendix F (page 137) to learn more about default role assignments and the full set of services
provided by each role.
Table 1-2 Role and Service Placement for Improved Availability
Special Considerations for Role Assignment
Service is Delivered in This
RoleService Name
The dbserver service is present on the head node by default and cannot
be moved. Thus, to achieve improved availability of the dbserver service,
the following is required:
• You must install and configure the HP StorageWorks Scalable File Share
(SFS) software, which must be purchased separately from HP.
When improved availability is enabled, the database tables are moved
to the system-wide /hptc_cluster file system (rather than the default
location in the /var/lib/mysql directory). In order for
/hptc_cluster to be highly available, it must reside on an SFS server.
• You must configure the head node into an availability set with one
additional node.
• You must assign the avail_node_management role to the additional
node.
For more information about the avail_node_management role, see
“Avail_node_management Role” (page 138).
avail_node_management
Database server
(dbserver)
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.
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.
For more information about the login role, see “Login Role” (page 140).
login
Linux Virtual Server
(LVS) director
Availability Tools from Other Vendors 29