Week 10 - NLB and Clustering.pptx

Week 10: NLB and Clusters NTWK-8070: Windows Server Roles and Features This week… This week we will learn about: • NLB • Server Clustering NLB – Network Load Balancing What is the NLB The NLB is a Server Feature that is installed after a role. The NLB is meant to facilitate a number of benefit...

Week 10: NLB and Clusters NTWK-8070: Windows Server Roles and Features This week… This week we will learn about: • NLB • Server Clustering NLB – Network Load Balancing What is the NLB The NLB is a Server Feature that is installed after a role. The NLB is meant to facilitate a number of benefits and is most often used with IIS (which we will explore in a later section) NLB stands for Network Load Balancing and is not only a server feature, but a industry technology (general term, we will focus on this) What is a Server Cluster A server cluster is simply a number of servers that are grouped by a common application or role. This can be a web server, a database server, a mail server, but not a mix. Windows NLB Installation Installing – Part 2 As we discussed, PowerShell can be used to administer all aspects of the server, including the installation of NLB Install-WindowsFeature NLB IncludeManagementTools What is NLB Used for? NLB is used for managing traffic flow, and ensuring that services remain available and accessible. NLB can help ensure: • Your services remain available during spikes in demand • Your services remain online during a server outage (partial cluster outage) How Load Balancing Works Source: https://www.nginx.com/resources/glossary/load-balancing/ Load Balancing Breakdown Load Balancing, in a nutshell, groups physical, or virtual servers into a cluster, which is able to distribute demand. A server cluster essentially acts as a group of servers that are clustered by a common application. A common example are Web Servers. Load Balancing Questions A single Web Server, no matter how powerful, is still limited in capacity. • How do we overcome multiple websites mapped to a single IP address? • How do we handle an increase in demand by adding more servers? • How do we ensure resilience and uptime during failures, planned or unplanned maintenance? The answer: Load Balancing Load balancing, as stated, groups servers together, by role, to ensure that these groups – known as Server Clusters, are able to act as one single entity. Clients then access this cluster through a load balancer, that determines what client goes to what server (in the cluster), and, is able to ensure high availability by monitoring server status (if a server is down, all traffic will be routed accordingly) Load Balancing as a Technology While Microsoft includes a Network Load Balancer – it is limited in it’s feature set. There are numerous disadvantages to using the NLB Feature, over a dedicated Load Balancer. A Dedicated Load Balancer works the same way as Windows NLB, however offers far more robust and can perform a significant number of additional features. Examples of Network Load Balancers Load Balancer Benefits There are numerous Load Balancing benefits, including: • Reducing application/service downtime – By routing requests to a less-utilized server, or, in the case of an outage, to a working one • To ensure scalability – By either routing requests to different geographical areas, or by giving you the flexibility to increase your service capacity by adding servers when the need to grow surfaces Hardware versus Software Load Balancers Load Balancers typically come in two flavours – software and hardware, both of these do the same thing (route and distribute traffic according to set parameters), however are different in their implementations. Before you continue… If you want to play with an industry standard load balancer, you can get started with one free of charge. While outside the scope of this course, it is still a good starting point. https://freeloadbalancer.com/ Hardware Load Balancers A hardware load balancer is much like a piece of networking equipment – much like a router or a switch. It typically allows for physical interfaces to be connected, allowing you to leverage high performance (multi-gigabit connectivity) Benefits of a Hardware LB Benefits to a hardware LB is that they are optimized for one task – load balancing. Specialty software and hardware comprise this unit, in order to allow for maximum and optimal traffic flow. Custom designed processors are able to process traffic much faster than a software load balancer. Software Load Balancers Software LBs are just that – and are typically used in virtual deployments. They route traffic based on criteria, and target server clusters. They are usually not as highperformance as hardwarebased LBs, but benefit from easier deployment and scale much easier. Load Balancing Methods Round Robin: This load balancing method is the simplest one of all – the server allocates requests in the order which they are received. For example, we have 3 servers in our cluster, and 6 client requests, each new request would go to a new server. Request 4 will go to Server 1, and the cycle starts over. This essentially distributed load equally. Methods Cont’d Intelligent Round Robin: While this can be known by many names (weighted, etc) – the gist of it is that requests are given a weight, priority or other criteria. This allows certain requests to prioritize a certain server. Methods Cont’d 2 Least Connections: Not all requests and connections last the same time – think of a website, some users may be on a website longer than others. This may mean that one sever is getting more requests than another. Least Connections will determine what server is least utilized Other Methods Many vendors implement specific algorithms that control how load balancing works. Required Reading Required Reading - Microsoft Please visit the links in the section “Required Reading” and read them. While this information is not on the test, it is crucial to your overall understanding, and an assignment for the NTWK-8090 course. End of Lecture, Questions?