VERITAS Storage Foundation 4.1 for Oracle RAC HP Serviceguard Storage Management Suite Extracts, December 2005

Storage Foundation for Oracle RAC Overview
Communications Stack Overview
RAC
ODM
CFS
CVM
SG/SGeRAC Core
GAB LLT
RAC
ODM
CFS
CVM
SG/SGeRAC Core
GAB
LLT
Cluster State
Cache Fusion/Lock Mgmt
Datafile Management
File System MetaData
Volume Management
The diagram above shows the data and communications stacks. Each of the components
in the data stack requires communications with its peer on other systems to function
properly. RAC instances must communicate to coordinate protection of data blocks in the
database. ODM processes must communicate to coordinate data file protection and access
across the cluster. CFS coordinates metadata updates for file systems, and CVM
coordinates the status of logical volumes and distribution of volume metadata across the
cluster. Serviceguard extension for RAC controls starting and stopping of components in
the Storage Foundation for Oracle RAC stack and provides monitoring and notification on
failure. SGeRAC must communicate the status of its resources on each cluster node. For the
entire system to work, each layer must communicate properly.
The diagram also shows Low Latency Transport (LLT) and Group Membership
Services/Atomic Broadcast (GAB), which make up the communications package central
to the operation of Storage Foundation for Oracle RAC. During an operational steady state,
the only significant traffic through LLT and GAB results from Lock Management and
Cache Fusion, while the traffic for the other data is relatively sparse.
Chapter 1, Overview: Storage Foundation for Oracle RAC 5