• Introduction • Load balancing • Clustering
• Server cluster is used to provide failover support for applications and services. • A Server cluster can consist of several nodes (computers). • Each node is attached to one or more cluster storage devices. • Cluster storage devices allow different servers to share the same data,and by reading this data provide failover for resources.
• Load balancing is used to scale the system as the client requests are increased • It is suitable for static data which can be copied to several load balancing servers • Each server is autonomous which means they don’t share any state information
• A farm is a group of servers that run similar services,but do not typically share data. • They are called a farm because they handle whatever requests are passed out to them using identical copies of data that is stored locally. • Because they use identical copies of data (rather than sharing data), members of a farm operate autonomously and are also referred to as clones. • Front-end Web servers running Internet Information Services (IIS) and usingNLB are an example of a farm.
• A pack is a group of servers that operate together and share partitioned data. • They are called a pack because they work together to manage and maintain services. • Because members of a pack share access to partitioned data, they have unique operations modes and usually access the shared data on disk drives to which all members of the pack areconnected. • An example of a pack is a database Server cluster running SQL Server 2000 and a server cluster with partitioned database views. Members of the pack share access to the data and have a unique chunk of data or logic that they handle, rather than handling all data requests. • In a 4-node SQL Server cluster:
– – – – Database Server 1 may handle accounts that begin with A-F. Database Server 2may handle accounts that begin with G-M. Database Server 3 may handle accounts that begin with N-S. Database Server 4 may handle accounts that begin with T-Z.
• Server clusters can be setup using many different configurations. • Servers can be either active or passive, and different servers can be configured to take over the failed resources of another server. • Failovercan take several minutes, depending on the configuration and the application being used, but is designed to be transparent to the end-user.
The Big Picture
Network Load Balancing Cluster Service
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IIS Web Server or other IP based services Data Servers SQL, Exchange, File
Clustering – more detailed picture
AddressingConcerns • Scalability
– Scale Up – Scale Out
– 99.9% Uptime
– Remote – UI and Command line
• MSCS – Server clusters provide failover of resources representing services, applications and base system features between the servers in the Cluster. NLB – (WLBS) Network Load Balancing clusters distribute client requestsor TCP/IP network traffic among many servers in the Cluster. Cluster – A group of independent computers that work together to run a common set of applications and provide the image of a single system to the client and application. Nodes or Hosts – Each system in a cluster configuration.
Client PCs Public network Private network (heartbeats,status, control) Cluster servers
Multi-initiator SCSI or SCSI over Fibre Channel
RAID disk sets
Recommended Environments • • • • • • Microsoft SQL Server™ 6.5 & 7.0 Microsoft Exchange 5.5 File shares Printer shares Other cluster-aware applications & services Typical uses are for data that changes frequently and cannot be easily replicated.
Network Load Balancing
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