Databases
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    <p><code>which figures of reference do you use?</code></p> <p>There is really only one figure that needs to be looked at, and then extrapolated on: data. All figures will derive from data requirements. </p> <p><em>Small example</em>: A billion requests per hour for an 8 byte binary number will not crash anything and could be run from the simplest of web servers. The reason for this is that the request time will be fractions of milliseconds. There are 1000 (ms/s) * 60 (s/m) * 60 (m/h) * 24 (h/d) = 86.4 million milliseconds in one day, meaning that even if each request took a full millisecond the 1 million required would still be available as the required speed for getting the 8 bytes would be in the 8kb/s range.</p> <p><em>Real life version</em>: Looking at the data will determine the requirements, and the data that is being retrieved is almost always in a database. The design of the database (even if conceptually) can help to determine how much data will be being used. There are multiple requirements in real life. The max capacity of the database, or filesystem, should be examined. This capacity can be calculated by looking at how much space each row of a table will require, by summing up the total space consumed by each column (i.e. an id of type int with length 6 will take 6 bytes or space). After summing each column of one row of a table, for each table in the database, it will be easy to tell how much memory each collection of tables will require (usually tables are linked through foreign keys). After the table memory consumption is considered, the users must then be examined for requirements. Mainly of interest is how many tables each user will be accessing per session (with no data this will be an guesstimation - best to overestimate). Because we already know, or have a good idea, what the size of the database tables are we can assume how much server memory the user will require. Comparing this memory usage to the amount of expected users will help to determine which server to use, or how many. Next to figure out is how many tables will be (again, on average guesstimation, or with some collected test data) inserted into the database as a result of user actions. This is very speculative and is best to be done with testing. Without testing, assumptions should be overestimated. Based off of how many rows each user will be inserting, it will be possible to extrapolate the database size and the bandwidth requirements. These will be determined through expanding the data requirement of one user, to the requirements of n users per t time. The data required by n users will make it possible to see bandwidth requirements over t time, and will also determine how n users will grow the database over t time.</p>
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    1. POHow do you do website capacity planning?
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    1. CO84 million ms/day
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      1. USCris Stringfellow
    2. COBad, bad example. Do you have any idea how many bytes the size of a request is? And how large a response is? Even if it only contains one byte of payload? And the number of packets needed to build up a http connection?
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      1. USStephan Eggermont
    3. COA request/response, and "build up of http connection", are surely references to the TCP handshake. Because the footprint of the handshake tends to be insignificant in actual use, it was not included in the *small* example.
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