Load Balancer Interview Questions & Answers part 2

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Q: – What is meant by dynamic and static content? Can my Array appliance cache dynamic content?

When a client requests a web page, a web server returns the requested content. If the content is retrieved from disk/memory and returned to the client without further processing, the content is said to be static. If the content is generated on-the-fly by the server (e.g., based on database data), it is referred to as dynamic content.

Q: – What is recursion depth?

In a tree structure, it refers to the number of levels that can be traversed below the main or parent page. This is often used to specify how much of a web site (how many levels deep) to preload into the cache.

Q: – How does the Cache decide what to cache?

The HTTP Cache-Control header determines the cacheability of the object and can also determine how long the object should be cached. The cache can be configured to override the cacheability of an object by specifying the hostname and a regular expression that matches within the URL of the object.

Q: – What algorithms are used for cache content replacement?

The Array(Hardware loadbalancer) Cache uses several algorithms for determining cache replacement behavior, depending on the context. In most cases, the Array will use LRU (Least Recently Used) to remove older content when space is needed.

Q: – What is Real Clustering?

Real clustering allows all configurations from all appliances in the cluster to be synchronized. Of course, only global parameters such as the SLB configuration are synchronized. Local parameters such as interface IP addresses are not synchronized.

Q: -What is Virtual Clustering?

Virtual clustering provides fault tolerance for VIPs among cluster members. For example, if an appliance is handling traffic and it fails, another appliance in the cluster will take over traffic processing.

Q: – How does virtual clustering work?

In a cluster of Array appliances(h/w load balancer), one appliance becomes Master for a particular VIP and handles all traffic related to that VIP. All others stay in Backup status. If the appliance containing the Master fails, one of the appliances in Backup status changes to Master status. Note: If multiple VIPs are configured, then Masters can be configured so that they are distributed among the appliances in the cluster, providing additional performance.

Q: – What parameters need to be defined in the cluster configuration?

Cluster ID, VIP address, interface (Outside or Inside), priorities, and authorization method (password or none) must be defined. Preempt and mrthresh are optional.

Q: – What is the purpose of Content Rewrite?

The Content Rewrite function allows CDN (Content Distribution Network) reference strings to be dynamically inserted into URLs that are embedded in web pages. With respect to one particular CDN, the term "linux" refers to the rewriting of embedded URLs to point to ubuntu-linux"s network.

 

Submitted By:-Nitu Chabra            Email-ID: – nituchabra@mail.com

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