Cluster Server 7.4.1 Administrator's Guide - Linux
- Section I. Clustering concepts and terminology
- Introducing Cluster Server
- About Cluster Server
- About cluster control guidelines
- About the physical components of VCS
- Logical components of VCS
- Types of service groups
- About resource monitoring
- Agent classifications
- About cluster control, communications, and membership
- About security services
- Components for administering VCS
- About cluster topologies
- VCS configuration concepts
- Introducing Cluster Server
- Section II. Administration - Putting VCS to work
- About the VCS user privilege model
- Administering the cluster from the command line
- About administering VCS from the command line
- About installing a VCS license
- Administering LLT
- Starting VCS
- Stopping the VCS engine and related processes
- Logging on to VCS
- About managing VCS configuration files
- About managing VCS users from the command line
- About querying VCS
- About administering service groups
- Modifying service group attributes
- About administering resources
- Enabling and disabling IMF for agents by using script
- Linking and unlinking resources
- About administering resource types
- About administering clusters
- Configuring applications and resources in VCS
- VCS bundled agents for UNIX
- Configuring NFS service groups
- About NFS
- Configuring NFS service groups
- Sample configurations
- About configuring the RemoteGroup agent
- About configuring Samba service groups
- About testing resource failover by using HA fire drills
- Predicting VCS behavior using VCS Simulator
- Section III. VCS communication and operations
- About communications, membership, and data protection in the cluster
- About cluster communications
- About cluster membership
- About membership arbitration
- About membership arbitration components
- About server-based I/O fencing
- About majority-based fencing
- About the CP server service group
- About secure communication between the VCS cluster and CP server
- About data protection
- Examples of VCS operation with I/O fencing
- About cluster membership and data protection without I/O fencing
- Examples of VCS operation without I/O fencing
- Administering I/O fencing
- About the vxfentsthdw utility
- Testing the coordinator disk group using the -c option of vxfentsthdw
- About the vxfenadm utility
- About the vxfenclearpre utility
- About the vxfenswap utility
- About administering the coordination point server
- About configuring a CP server to support IPv6 or dual stack
- About migrating between disk-based and server-based fencing configurations
- Migrating between fencing configurations using response files
- Controlling VCS behavior
- VCS behavior on resource faults
- About controlling VCS behavior at the service group level
- About AdaptiveHA
- Customized behavior diagrams
- About preventing concurrency violation
- VCS behavior for resources that support the intentional offline functionality
- VCS behavior when a service group is restarted
- About controlling VCS behavior at the resource level
- VCS behavior on loss of storage connectivity
- Service group workload management
- Sample configurations depicting workload management
- The role of service group dependencies
- About communications, membership, and data protection in the cluster
- Section IV. Administration - Beyond the basics
- VCS event notification
- VCS event triggers
- Using event triggers
- List of event triggers
- Virtual Business Services
- Section V. Veritas High Availability Configuration wizard
- Introducing the Veritas High Availability Configuration wizard
- Administering application monitoring from the Veritas High Availability view
- Administering application monitoring from the Veritas High Availability view
- Administering application monitoring from the Veritas High Availability view
- Section VI. Cluster configurations for disaster recovery
- Connecting clusters–Creating global clusters
- VCS global clusters: The building blocks
- About global cluster management
- About serialization - The Authority attribute
- Prerequisites for global clusters
- Setting up a global cluster
- About IPv6 support with global clusters
- About cluster faults
- About setting up a disaster recovery fire drill
- Test scenario for a multi-tiered environment
- Administering global clusters from the command line
- About global querying in a global cluster setup
- Administering clusters in global cluster setup
- Setting up replicated data clusters
- Setting up campus clusters
- Connecting clusters–Creating global clusters
- Section VII. Troubleshooting and performance
- VCS performance considerations
- How cluster components affect performance
- How cluster operations affect performance
- VCS performance consideration when a system panics
- About scheduling class and priority configuration
- VCS agent statistics
- About VCS tunable parameters
- Troubleshooting and recovery for VCS
- VCS message logging
- Gathering VCS information for support analysis
- Troubleshooting the VCS engine
- Troubleshooting Low Latency Transport (LLT)
- Troubleshooting Group Membership Services/Atomic Broadcast (GAB)
- Troubleshooting VCS startup
- Troubleshooting issues with systemd unit service files
- Troubleshooting service groups
- Troubleshooting resources
- Troubleshooting sites
- Troubleshooting I/O fencing
- Fencing startup reports preexisting split-brain
- Troubleshooting CP server
- Troubleshooting server-based fencing on the VCS cluster nodes
- Issues during online migration of coordination points
- Troubleshooting notification
- Troubleshooting and recovery for global clusters
- Troubleshooting licensing
- Licensing error messages
- Troubleshooting secure configurations
- Troubleshooting wizard-based configuration issues
- Troubleshooting issues with the Veritas High Availability view
- VCS message logging
- VCS performance considerations
- Section VIII. Appendixes
About LLT flow control tunable parameters
Table: LLT flow control tunable parameters lists the LLT flow control tunable parameters. The flow control values are set in number of packets. The command lltconfig -F query can be used to display current flow control settings.
Table: LLT flow control tunable parameters
LLT parameter | Description | Default | When to change | Dependency with other LLT tunable parameters |
---|---|---|---|---|
highwater | When the number of packets in transmit queue for a node reaches highwater, LLT is flow controlled. | 200 | If a client generates data in bursty manner, increase this value to match the incoming data rate. Note that increasing the value means more memory consumption so set an appropriate value to avoid wasting memory unnecessarily. Lowering the value can result in unnecessary flow controlling the client. | This flow control value should always be higher than the lowwater flow control value. |
lowwater | When LLT has flow controlled the client, it will not start accepting packets again till the number of packets in the port transmit queue for a node drops to lowwater. | 100 | Veritas does not recommend to change this tunable. | This flow control value should be lower than the highwater flow control value. The value should not be close the highwater flow control value. |
rporthighwater | When the number of packets in the receive queue for a port reaches highwater, LLT is flow controlled. | 200 | If a client generates data in bursty manner, increase this value to match the incoming data rate. Note that increasing the value means more memory consumption so set an appropriate value to avoid wasting memory unnecessarily. Lowering the value can result in unnecessary flow controlling the client on peer node. | This flow control value should always be higher than the rportlowwater flow control value. |
rportlowwater | When LLT has flow controlled the client on peer node, it will not start accepting packets for that client again till the number of packets in the port receive queue for the port drops to rportlowwater. | 100 | Veritas does not recommend to change this tunable. | This flow control value should be lower than the rpothighwater flow control value. The value should not be close the rporthighwater flow control value. |
window | This is the maximum number of un-ACKed packets LLT will put in flight. | 50 | For performance reason, the adaptive window feature is enabled, by default for port 5 (cfs) and port 24(cvm). You can manually enable adaptive window for other ports by changing the value of the LLT_AW_PORT_LIST parameter in the /etc/sysconfig/llt file.
Change the value as per the private networks speed. Lowering the value irrespective of network speed may result in unnecessary retransmission of out of window sequence packets. | This flow control value should not be higher than the difference between the highwater flow control value and the lowwater flow control value. The value of this parameter (window) should be aligned with the value of the bandwidth delay product. |
linkburst | It represents the number of back-to-back packets that LLT sends on a link before the next link is chosen. | 32 | For performance reasons, its value should be either 0 or at least 32. | This flow control value should not be higher than the difference between the highwater flow control value and the lowwater flow control value. |
ackval | LLT sends acknowledgement of a packet by piggybacking an ACK packet on the next outbound data packet to the sender node. If there are no data packets on which to piggyback the ACK packet, LLT waits for ackval number of packets before sending an explicit ACK to the sender. | 10 | Do not change this value for performance reasons. Increasing the value can result in unnecessary retransmissions. | Not applicable |
sws | To avoid Silly Window Syndrome, LLT transmits more packets only when the count of un-acked packet goes to below of this tunable value. | 40 | For performance reason, its value should be changed whenever the value of the window tunable is changed as per the formula given below: sws = window *4/5. | Its value should be lower than that of window. Its value should be close to the value of window tunable. |
largepktlen | When LLT has packets to delivers to multiple ports, LLT delivers one large packet or up to five small packets to a port at a time. This parameter specifies the size of the large packet. | 1024 | Veritas does not recommend to change this tunable. | Not applicable |