Note that you will have to design a protocol for saving the data into the array

Note that you will have to design a protocol for

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Note that you will have to design a `protocol' for saving the data into the array. The disk array is just an array of characters, you if you want to save a file, you need to know what is data corresponding to which file. Hint: you might want to limit the filename size to, say, eight characters to make the problem easier, like in DOS. Explain carefully how you locate files on your disk, and what scheme your filesystem uses to recover files in the correct order. 6. Networks: Services and protocols In this section we shall consider how to use the concepts we have considered so far to make the task of implementing network communication as straightforward as possible. Consider a large company or a university with thousands of users, many of whom have workstations or terminals on their desks - all of whom are connected to a network. In this situation it is natural to share certain resources so that they can be accessed from anywhere on the network, without having to be reproduced on every machine: The printer, User authentification data (password database), Disks holding user data, A reference clock which can be used to set the local clocks on all systems, Addresses and telephone numbers. To some extent, this idea of sharing was the idea behind multi-user systems. Not everyone can afford their own - so we share. What big multiuser mainframe machines have tought us, however, is that a single monolithic computer with terminals is not a good solution. Users demand more and more CPU power every day. Scheduling the CPU, even if efficient on paper, can be spoiled in practice for most users by a few greedy users. Everyone wants their own private CPU. Interactive I/O places a big load, proportional to the number of users. A large machine with a hundred keyboards attached to it can quickly become overwhelmed by keyboard I/O. More and more programs are interactive and the I/O overhead is much larger since mice and windows came along. The solution which is popular at present is to give everyone a smaller machine with their own CPU, keyboard and screen. Although perhaps wasteful in theoretical terms, in practice it is one of those little luxuries, like owning a big car, which improves the quality of life for those who have it. What's more, since computing power has generally increased, software has grown to absorb that power - so it is not wasted for long.
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By giving everyone their own machine, linked together by a network we Spread the interactive I/O load over all the machines. Allow machines to have public and private resources. Introduce a new overhead: the network software. 6.1 Services: the client-server model To share public resources on a network, we introduce the concept of a service . A service is simply a job done by one part of a system on behalf of another. The service is provided by a server on behalf of a client . This is what is known as the client server model 6.1 .
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