Load Balancing Flashcards
(19 cards)
What is a load balancer?
spreads traffic across a cluster of servers
What are some benefits of using a load balancer?
improves responsiveness, availability
Where can I put load balancers?
- between user and web server
- between web server and internal platform layer
- between internal platform layer and database
Least Connection Method
directs traffic to server with fewest active connections
Least Response Time Method
directs traffic to server with fewest active connections and lowest average response time
Least Bandwidth Method
directs traffic to server that is currently serving the least amount of traffic, measured in mbps
mbps
megabits per second
Round Robin Method
cycles through a list of servers and sends each new request to the next server
Weighted Round Robin Method
designed to handle servers with different processing capacity. Servers with higher weights receive new connections first and more connections than those with lower weights
IP Hash Method
calculates a hash of the IP address to determine which server receives the request
When should you use the Least Connection Method?
when there are a large number of persistent connections unevenly distributed between the servers
When should you use the Round Robin Method?
when the servers are of equal specification and there are not many persistent connections
Smart Client
add LB algorithm to a client side application or database client
What are some benefits to a Smart Client implementation?
It’s easy to implement and manage for small systems
What are some tradeoffs with a Smart Client implementation?
when the system gets bigger it gets more complex and harder to manage, usually requires a standalone server
Hardware Load Balancer
highly performant, hardware solution like Citrix NetScalar, generally used as a first point of contact for user requests and use other approaches for balancing traffic within the network
What are some benefits to a Hardware Load Balancer?
highly performant
What are some tradeoffs with a Hardware Load Balancer?
expensive and difficult to configure
Software Load Balancer
hybrid of a smart client and hardware load balancer. run on the same machine as the client or server application and acts as a proxy, so every request coming into the application will be received and passed to the backend service in an efficient way
