System Architecture

This is a conversation between my best friend and me.

(The phone rings : tring tring…tring tring…. Tring tring…. Tring tring)

Me : “Hello”!

Ria: “Finally! You picked up. Whats wrong with your phone? I called you about a hundred times yesterday. To tell you that I have booked tickets for ‘The Dark Knight Rises’.  10 am show today at PVR. Don’t even think of making excuses. The whole group is coming”

Me : “Ria, chill girl! I’ll try to come but no promises. Got an MIS assignment to submit before 10 am today. If I complete that by 9 am, I’ll come ok.”

Ria : “NO WAY! Whatever is your assignment, I’ll help you with it. What is it on?”

Me : “On your favourite topic: System Architecture.” Come over and teach me the basics. That way I can get it doon soon and we’ll be off for the movie by 9”

Ria : “Coming right away”

(Knock knock…. I let Ria in and we start off with my assignment)

Me : “Ya, I just started with the system architecture! What exactly does single tier, two-tier, three tier etc mean? "

Ria : “Well, single tier architecture was mainly used in times of huge mainframes. All the processing was done on a single computer and all the resources are attached to the same computer. The advantages of such a system would be that its simple and efficient but the cost of such a a machine would be very high.

Me : So an ideal pictorial representation would be like this?

Ria : Yep! Now in a two-tier architecture, the user system interface is usually located on the users desktop environment and the database management services are usually in a more powerful machine that serves many clients. But the problem with this model was that the connections were very expensive.

Me : How secure is this? Can multiple users access the database at the same time?

Ria : As the client computer usually can’t see the database directly and can only access the data by starting the client. This means that the data on the server is much more secure. Also users are unable to change or delete data unless they have specific user rights to do so. And yes, multiple users can access the database a at the same time as long as they are accessing data in different parts of the database.

Me : Hmmm! So let me guess – the three tier architecture will have three layers and the data will probably be  even more secure in this model?

Ria : True. With the advent of internet, many people jumped to the conclusion that the days of mainframes were back. The Client/ Server model had obviously failed, PC’s had failed and Windows were on its way out. A host of thin client applications were developed and thus the 3-tier architecture was born. This is basically the traditional client/ server model run from a web server.

Me : So, its something like a three way interaction in a client server environment? Wherein the user interface is stored in the client, the data is stored in the database server and the Business application logic is stored in yet another server or something?.

Ria : Good! Your catching on. Also remember, as more users can access the system, a 3-tier system is more scalable than the other solutions because we can add multiple middle tiers, each running on their own server’s, to ensure a good performance ( N-tier ) and there is increased security as the database is hidden form the client. But on the downside, it is more difficult to build than a 2-tier model.

Me : Got it. Give me half an hour. Let me just post this on my blog. And off we go for Dark Knight Rises.