CHOOSING A WEB HOST: PART 3
WHY MOST HOSTS PREFER TRANQUIL SITES
Interview with Will Bontrager
Q. Some people want sites based on "x" megs of space and "x" gigs
of
traffic. What's the difference?
A. Space refers to how much total space your files take up on the
server. Traffic (in this case) refers to the total bytes that was
sent
to browsers. (Usually, the bytes of traffic are identical to the size
of the file sent to browsers multiplied by the number of times the
file was sent.) Sometimes traffic is expressed as "# per day" and
sometimes as "# per month." If measured, it must be measured within a
specific time period.
A gigabyte is just a tad over a thousand megabytes, I think. So if
all the files of your site, HTML and images and every other file
that makes up your public site, is 10 mg total and if every file is
sent to browsers 1000 times in one day, then you have had 10 gigs of
traffic during that day.
In practice, some files are sent to browsers more often than
others.
Large image, sound, or multi-media files can take up a lot of space
on
the server. Those same files, if they're sent to browsers very often,
add to a lot of your traffic. But if they're rarely sent to browsers,
they take up server space but don't significantly affect your
traffic.
There is a third item that hosting companies watch: CPU usage.
CPU is
the computer's processing unit, the processor from Motorola or Intel
or other manufacture inside every computer. CPU usage is a
measurement
of the amount of time the processing unit is used.
This is a critical measurement for hosting companies because
installing bigger hard drives or getting more telephone lines will
not provide more CPU. There's only so much of it available in each
server, and no more, like there are only 24 hours in a day.
If your site happens to be on a slow server, it could be your
internet connection or heavy internet traffic. But more likely it
is a shortage of CPU on the server itself. This happens when a
hosting company puts too many internet sites on the same server
or when one/several sites on the server require a lot of CPU.
HTML web pages and images require very little CPU, so little that
it's often not measured. However, sending content to browsers that
requires running a program on the server can, depending on the
program, be CPU intensive. These include RealAudio, ASP, PHP, and
other technologies.
I am a CGI professional, so I'll use CGI programs as examples.
If the CGI program is written with Perl, a Perl
compiler/interpreter
must be launched every time the Perl script is launched. The compiler
/interpreter is necessary in order to translate and run the plain
text script. (An exception would be if your hosting company provided
and you used mod_perl, a system that allows the compiler/interpreter
and your script to remain in memory even while they're not being
used.)
The compiler/interpreter might take a second to launch. This
shouldn't
be significant unless you run thousands of Perl scripts every
day.
With Perl, the scripts are the wild variables. Some, probably
most,
do their job and quit within a second or two, or even a fraction of a
second. Again, this can become significant if your script runs
thousands of times a day.
Some scripts run for many minutes at a time. These use a lot of
CPU.
An example is a list server that is doing a mailing. (Note: some
hosting companies configure their servers so scripts running longer
than a set amount of time are automatically killed -- made to quit
and kicked out of memory.)
If you're only moderately successful and your site doesn't
require a
lot of CPU intensive content delivery, then this is not something you
should have to take into consideration. However, if you become wildly
successful, then watch out.
We have had two clients, each with a different hosting company,
experience high success and being forced off their servers. In one
case, the client was given 24 hours to move either to a dedicated
server leased from the hosting company or to a different hosting
company altogether. This was a "survival" site (with some focus on
the upcoming year 2000); it didn't have many individual CGI scripts
but did have a lot of traffic so the scripts got much use. The other
client's site was a URL redirection site, had lots of CGI, and
experienced sudden success. This site received a week's notice, but
otherwise the same options as the first.
You see, with several hundred relatively tranquil sites on one
server,
when yours suddenly becomes successful and uses most of the available
CPU, then 199 customers are mad at the hosting company. So the
hosting company has to get rid of you in order to please the
others.
You'll almost always find some reference to CPU usage or server
resources in hosting companies' terms of service or other documents
they say you are bound to, even hosting companies who boast unlimited
traffic and gazillions of megabytes of disk space. Sometimes it's
hidden away, but it's almost always there somewhere.
Hosting companies rarely admit it, but they like tranquil sites.
That's
where their money is. Your money, however, probably depends on an
active
site.
So be aware that when you become successful, your hosting company
will
probably require you to do something to accommodate your higher CPU
requirements.
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