vcs building blocks. topic 1: cluster terminology after completing this topic, you will be able to...
DESCRIPTION
A Nonclustered Computing EnvironmentTRANSCRIPT
VCS Building Blocks
Topic 1: Cluster Terminology
After completing this topic, you will be able to define clustering terminology.
A Nonclustered Computing Environment
Definition of a Cluster
A cluster is a collection of multiple independent systems working together under a management framework for increased service availability.
Application
Node
Storage
Cluster Interconnect
Definition of VERITAS Cluster Server and Failover
VCS detects faults and performs automated failover.
Application
Node
Failed Node
Storage
Cluster Interconnect
Definition of an Application Service
An application service is a collectionof all the hardware and software components required to provide a service. If the service must be migrated to
another system, all components need to be moved in an orderly fashion.
Examples include Web servers, databases, and applications.
Definition of a Service Group
A service group is a virtual containerthat enables VCS to manage an application service as a unit. All components required to
provide the service, and the relationships between these components, are defined within the service group.
A service group has attributes that define its behavior, such as where it can start and run.
Service Group Types Failover:
– The service group can be online on only one cluster system at a time.
– VCS migrates the service group at the administrator’s request and in response to faults.
Parallel– The service group can be online on multiple cluster
systems simultaneously.– An example is Oracle Real Application Cluster (RAC).
HybridThis is a special-purpose type of service group used to manage service groups in replicated data clusters (RDCs). RDCs use replication between systems at different sites instead of shared storage.
Definition of a ResourceResources are VCS objects that correspond to thehardware or software components of an applicationservice. Each resource must have a unique name throughout the
cluster. Choosing names that reflect the service group name makes it easy to identify all resources in that group, for example, WebIP in the WebSG group.
Resources are always contained within service groups. Resource categories include:
– Persistent None (NIC) On-only (NFS)
– NonpersistentOn-off (Mount)
Resource DependenciesResources in a service group have a defined dependency relationship, which determines theonline and offline order of the resource. A parent resource depends
on a child resource. There is no limit to the
number of parent and child resources.
Persistent resources, such as NIC, cannot be parent resources.
Dependencies cannot be cyclical.
Parent/child
Child
Parent
Resource AttributesResource attributes definean individual resource. The attribute values are
used by VCS to manage the resource.
Resources can have required and optional attributes, as specified by the resource type definition.
mount –F vxfs /dev/vx/dsk/WebDG/WebVol /Web
WebMount resource
Solaris
Resource TypesResources are classifiedby type. The resource type
specifies the attributes needed to define a resource of that type.
For example, a Mount resource has different properties than an IP resource.
mount [-F FSType] [options] block_device mount_point
Solaris
Agents have one or more entry points that perform a set of actions on resources.
Each system runs one agent for each active resource type.
Agents: How VCS Controls ResourcesEach resource type has a corresponding agent process that manages all resources of that type.
online
offline
monitor
clean
NIC
eri0
IP
10.1.2.3
Mount
/web /log
Volume
WebVol logVol
Disk Group
WebDG
Topic 2: Cluster Communication
After completing this topic, you will be able to describe cluster communication mechanisms.
Cluster Communication
The cluster interconnectserves to: Determine which systems are
members of the cluster using a heartbeat mechanism.
Maintain a single view of the status of the cluster configuration on all systems in the cluster membership.
A cluster interconnect provides a communicationchannel between cluster nodes.
Low-Latency Transport (LLT)
LLT
LLT
LLT: Is responsible for sending
heartbeat messages Transports cluster
communication traffic to every active system
Balances traffic load across multiple network links
Maintains the communication link state
Is a nonroutable protocol Runs on an Ethernet
network
Group Membership Services/Atomic Broadcast (GAB)
GAB: Performs two functions:
– Manages cluster membership; referred to as GAB membership
– Sends and receives atomic broadcasts of configuration information
Is a proprietary broadcast protocol
Uses LLT as its transport mechanism
LLTLLT
GAB LLT
GAB
The Fencing DriverFencing: Monitors GAB to detect
cluster membership changes
Ensures a single view of cluster membership
Prevents multiple nodes from accessing the same Volume Manager 4.x shared storage devices
LLT
GAB
Fence
Fence
LLT
GAB
Reboot
The High Availability Daemon (HAD) The VCS engine, the
high availability daemon:– Runs on each system
in the cluster– Maintains configuration
and state information for all cluster resources
– Manages all agents The hashadow daemon
monitors HAD.
HADhashadow
LLT
GAB
Fence
Comparing VCS Communication Protocols and TCP/IP
HADhashadow
LLT
GAB
iPlanet
NIC
TCP
IP
NIC
User Processes
Kernel Processes
Hardware
Topic 3: Maintaining the Cluster Configuration
After completing this topic, you will be able to describe how the cluster maintains the configuration.
Maintaining the Cluster Configuration HAD maintains a
replica of the cluster configuration in memory on each system.
Changes to the configuration are broadcast to HAD on all systems simultaneously by way of GAB using LLT.
The configuration is preserved on disk in the main.cf file.
HADmain.cf hashadow
HADhashadow
VCS Configuration Files
include "types.cf"cluster vcs (
UserNames = { admin = ElmElgLimHmmKumGlj }Administrators = { admin }CounterInterval = 5)
system S1 ()
system S2 ()
group WebSG (SystemList = { S1 = 0, S2 = 1 })Mount WebMount (
MountPoint = "/web"BlockDevice = "/dev/vx/dsk/WebDG/WebVol"FSType = vxfsFsckOpt = "-y")
main.cf
A simple text file is used to store the cluster configuration on disk.
The file contents are described in detail later in the course.
Topic 4: VCS Architecture
After completing this topic, you will be able to describe the VCS architecture.
VCS Architecture Agents monitor resources on
each system and provide status to HAD on the local system.
HAD on each system sends status information to GAB.
GAB broadcasts configuration information to all cluster members.
LLT transports all cluster communications to all cluster nodes.
HAD on each node takes corrective action, such as failover, when necessary.
Topic 5: Supported Failover Configurations
After completing this topic, you will be able to describe the failover configurations supported by VCS.
Active/Passive
Before Failover After Failover
Active/Passive N-to-1
Before Failover
After Failover
Before Failover
After Repair
Active/Passive N + 1
After Failover
Standby Server
Standby Server
Active/Active
Before Failover After Failover
N-to-N
Before Failover
After Failover