VERITAS Storage Foundation 4.1 Cluster File System HP Serviceguard Storage Management Suite Extracts, December 2005

About CFS
62 Installation and Administration Guide
Recovering from Jeopardy
The disabled file system can be restored by a force unmount and the resource can be
brought online without rebooting, which also brings the shared disk group resource
online. Note that if the jeopardy condition is not fixed, the nodes are susceptible to leaving
the cluster again on subsequent node failure. For a detailed explanation of this topic, see
the VERITAS Cluster Server User’s Guide.
Fencing
With the use of I/O enabled fencing, all remaining cases with the potential to corrupt data
(for which jeopardy handling cannot protect) are addressed.
Single Network Link and Reliability
Certain environments may prefer using a single private link or a pubic network for
connecting nodes in a cluster, despite the loss of redundancy for dealing with network
failures. The benefits of this approach include simpler hardware topology and lower costs;
however, there is obviously a tradeoff with high availability.
For the above environments, SFCFS provides the option of a single private link, or using
the public network as the private link if I/O fencing is present.
I/O fencing is used to handle
split-brain scenarios. The option for single network is given during installation.
Low Priority Link
LLT can be configured to use a low-priority network link as a backup to normal heartbeat
channels. Low-priority links are typically configured on the customer’s public or
administrative network. This typically results in a completely different network
infrastructure than the cluster private interconnect, and reduces the chance of a single
point of failure bringing down all links. The low-priority link is not used for cluster
membership traffic until it is the only remaining link. In normal operation, the
low-priority link carries only heartbeat traffic for cluster membership and link state
maintenance. The frequency of heartbeats drops 50 percent to reduce network overhead.
When the low-priority link is the only remaining network link, LLT also switches over all
cluster status traffic. Following repair of any configured private link, LLT returns cluster
status traffic to the high-priority link.
In HP Serviceguard Storage Management Suite environments, Serviceguard handles the
configuration and control of LLT.