How Much Bandwidth Do You Need?
Server bandwidth is the single most important factor in the performance of your web site. The math to determine what bandwidth you need is, in essence, very simple:
hits/second * average size of a hit in bits = bits/second
That is, you need some estimate of the number of hits per second you want to be able to serve. Then you need to know the average size of one of these hits. From this, you know what sort of network bandwidth you need.
Thinking About Bandwidth
You can get some perspective when thinking about bandwidth from the following chart. Note that Table 2.1 uses the decimal million (1000000) and not “mega” which is 220 = 1048576.
Table 2-1. Bandwidth Comparison
|
Mode of data transfer |
Million bits/second |
Comments |
|---|---|---|
|
Fast typist |
0.000035 |
70 words/min × 5 chars/word × 6 bits/char × M/106 × min/60 seconds. |
|
4800bps modem |
0.004800 |
4800 bits/sec × M/106 This is also about maximum human reading speed. |
|
POTS sampling rate |
0.064000 |
Voice over plain old telephone service is sampled at 64kbps. |
|
ISDN, two channels bonded |
0.128000 | |
|
One million 10000-byte web hits in one day, evenly distributed |
0.925925 |
106 hits/day × 80Kbits/hit × day/86400 seconds × M/106. |
|
Audio CD |
1.280000 |
40000 samples/second × 16 bits/sample × 2 (stereo) × M/106. |
|
T-1 (DS-1 or primary ISDN) |
1.544000 |
Carries 24 POTS channels with 8kbps overhead. |
|
Ethernet |
10.00000 | |
|
Token Ring |
16.00000 | |
|
IDE Hard disk |
16.00000 |
Sustained throughput. |
|
T-3 (DS-3) |
44.60000 |
672 DS-0’s, 28 ... |
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