Resource Hierarchies - SIOS

SPS Configurations
alternative to the normal intelligent switchback behavior described above. This option can be selected
for individual resource hierarchies on individual servers. If automatic switchback is selected for a
resource hierarchy in the In-Service-Protected (ISP) state running on a given server and that server
fails, the resource hierarchy is failed over to a backup system; when the failed server recovers, the
hierarchy is automatically switched back to the original server.
Notes:
• If using data replication (DataKeeper), you must choose intelligent switchback. Automatic
switchback is not supported.
• Checks for switchback are only made either when LifeKeeper starts or when a new server is
added to the cluster; they are not performed during normal cluster operation.
• SPS never performs an automatic switchback from a higher priority server to a lower priority
server.
• If there is a dependency between two resources with different switchback strategies, the
switchback strategy of the parent resource takes precedence.
SPS Configurations
SPS works on the basis of resource hierarchies you define for groups of two or more servers. The
following three topics introduce the SPS failover configuration concepts.
• Common Hardware Components
• System Grouping Arrangements
• Resource Hierarchies
Common Hardware Components
All SPS configurations share these common components as illustrated in the diagram below:
1. Server Groups. The basis for the fault resilience provided by SPS is clustered Windows 2003
servers. The servers, also referred to as SPS nodes, do not have to be the same hardware
platform.
2. Communication paths for heartbeat. It is strongly recommended that each pair of servers in
the group share at least two communication paths (comm paths), although only one is
required. To avoid unnecessary failover due to communication failure, you should configure
your redundant comm paths using different protocols and communication media, for example
TCP/IP (or socket). SPS uses the comm paths to coordinate resource availability for the faultdetection
heartbeat, a periodic message between nodes and for switchover of resources. (See
Overview of Communication Paths.)
3. Shared data resources. SPS can recover and restore shared or mirrored data, applications
and communication resources. SPS controls access at the volume (drive letter) level. In case
of a server failure, SPS automatically switches availability of protected resources to an active
server. Peripheral devices that are to be shared between systems must be packaged in
external peripheral cabinets. See the Configuring Your Storage topic for information to help you
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