HP Serviceguard Extended Distance Cluster for Linux A.01.00 Release Notes, Second Edition, May 2008

HP Serviceguard Extended Distance Cluster for Linux Release Notes
Compatibility Information and Installation Requirements
Chapter 1 13
In this table, every node is followed by a node from another site. If this
order is not used, then site failures can result in data loss. In the event of
a site failure at site S1, if N1 goes down first followed by N2, it results in
a package failure. This failure occurs because after N1 fails, the package
may failover to N2 if the recommended order of configuration is not
specified. When the package fails over to N2 at the same site, it starts
with a partial mirror disk. Starting with a single mirror disk prevents
the package from starting at site S2 if N2 also fails. The package will not
start on a node in site S2 because XDC prevents starting a package that
has already started once before with a partial mirror disk.
For this reason, it is also required that if one node of the four nodes is
brought down at a site for maintenance, then one node at the other site
must also be brought down. So if a node in one site fails, the package will
fail over to another node in the other site.
IMPORTANT It is recommended that you maintain an equal number of nodes at both
sites during maintenance. However, this recommendation does not apply
to a 2-node cluster environment.
N3 Site 2
N2 Site 1
N4 Site 2
or
N1 Site 1
N4 Site 2
N2 Site 1
N3 Site 2
Table 1-2 Failover Sequence (Continued)
Node Site