Database Reference
In-Depth Information
Chapter 9
Network Practices
by Riyaj Shamsudeen, Kai Yu
Reliable and scalable network architecture is a critical element in Real Application Cluster (RAC) infrastructure
design. The availability of applications in a RAC database depends heavily on the reliability of the network
infrastructure. Many design aspects of a RAC cluster's underlying network should be considered before implementing
a cluster in a production environment, since making changes to the RAC cluster after production go-live is never easy.
As nodes in a cluster are monitored by exchanging short messages between the Clusterware daemons, any network
disconnect can lead to messaging failures, resulting in node restart or rebootless
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Clusterware restarts.
Cache fusion traffic flows through the private network too. Latency in private network traffic will lead to elevated
wait times for global cache events. Worse, dropped packets in the private network, due to problems in network
configuration, can result in much longer global cache event waits.
Types of Network
A typical organization has different kinds of networks, and network traffic usually is separated into different network
segments, possibly employing many physical infrastructure segments.
The
public network
is used primarily for general traffic such as applications connecting to a database, users
executing queries from an application screen, etc. For a public network, default network attributes are sufficient as
the default values are designed to match the traffic characteristics of public network traffic. Further, database listeners
listen on an IP address on the public network. A
storage network
is primarily used for communication between
servers and storage servers to support network-based storage. A
private network
is a special type of network used for
communication among cluster nodes in a RAC cluster.
Many organizations also employ a
backup network
primarily carrying backup data of applications and databases.
These networks also carry a huge amount of network traffic and might need further tuning to improve backup speed.
While many discussions in this chapter apply to all types of networks, the primary focus is on private networks.
Logically, there are two types of network packets flowing through a private interconnect: big packets with a database
block as payload, and small packets with short messages (~400 bytes) as payload. A private network must be tuned to
operate better for bigger workloads and to have very low latency. In most cases, private network traffic is contained
within a short network segment, that is, within a switch or two.
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Node reboots can be time-consuming and Clusterware tries to avoid them by restarting itself. Of course, a Clusterware restart will
cause databases and listeners to restart.
