
IBM eNetwork Communications Server for Windows NT
Host Publisher Feature, Version 6.01
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High Traffic Web Sites
You can use a variety of techniques to handle high traffic levels
on your web site with Host Publisher.
The general procedure should be:
- Estimate the amount of traffic your web site will handle
at peak load.
- Measure the performance of each component, using
your hardware, your network, and your data sources.
Some components to consider
are your web server, your network, your page
server, and whatever data sources your Page Server is using.
- Identify components that will need to be replicated or
to have their performance improved to meet your traffic
requirements.
- Plan and implement the necessary changes.
- Measure performance. Repeat until your performance
goals are met.
Most of this work is not specific to Host Publisher.
We will only go into details about Host Publisher.
Standard web techniques
Host Publisher uses standard web servers and can accept requests from
multiple web servers. Therefore, you can use industry-standard
techniques for improving your web server performance, including
tuning, caching, better hardware (computer and network), and
load-spreading products.
Page Server
There are a number of techniques that can be used to improve the
performance of a Page Server.
Hardware
The most important hardware component in a server machine is memory.
Memory is relatively inexpensive, especially when you consider how
much and how easily more memory can improve your server performance.
Consider 128M of memory to be the minimum for a modern server machine,
and add more memory freely as long as more memory continues to improve
performance.
Page Caching
The easiest way to improve page server performance is to turn on
page caching for all web pages that do not require instantaneously updated
data. Even if the cache timeout is only ten minutes, if a hundred
requests for the page occur each hour, 94 of them will be satisfied
from the cache instead of generating the web page again.
Caching will increase use of memory and disk space, and disk
traffic.
Java memory
Increasing the amount of memory available to Java can improve
the performance of Java-intensive SIMs, such as the Host Access SIM.
By default, Host Publisher gives Java 16M of memory. If you have a
lot of memory available, and you are using the Host Access SIM,
increasing this value can allow you to process more requests
simultaneously.
If Host Access page requests are failing with error messages
indicating lack of Java memory, you must increase this value or
decrease the number of Page Server threads.
Create a new registry entry under
HKEY_LOCAL_MACHINE\SOFTWARE\IBM\Host Publisher\Config
called JVMHeapSize. The entry should be a DWORD. Its value is the
Java memory size in megabytes. The default, if there is no registry
entry, is 16M.
Host Access performance
If you are using the Host Access SIM, consider
setting pages to
client scope
or using connection caching to improve performance
if appropriate.
Threads
The number of Page Server threads affects the Page Server's
performance, but not always in a straightforward way.
For example, if it takes 1 second to process a request, and
the Page Server has 5 threads, the Page Server's maximum
rate will be 5 requests per second.
If you increase the number of threads to 10, the Page Server might
process 10 requests per second. But if the requests are CPU
or memory-intensive, processing 10 at the same time may slow down
the Page Server so it takes 3 seconds to process each request.
The rate will only be 3.3 requests per second, worse than before.
It is important to test Page Server performance after adjusting
the number of threads. Too many threads can be as bad as
too few.
More threads require more memory and CPU, and can increase
disk and network traffic.
Interaction of changes
These factors are all related. For example, after adding memory or
moving to a faster CPU, the Page Server might be able to run with more
threads. After changing any factor, reconsider the others.
One approach would be to install the fastest processor and the
most memory you can afford (focusing most on memory), turn on
page caching, and then use experimentation to determine the
optimum number of threads.
Traffic mix
If your site will serve some simple requests and some complicated
(and expensive) requests, consider assigning them to different
Page Servers. It is easier to plan your Page Server performance
if its work load is homogeneous.
Replication of Page Servers
Adding more Page Servers is an easy way to process requests
faster. If the Page Servers are using external data sources,
consider their ability to handle the load. You might need to
replicate the data sources or improve their performance in
order to handle the increased number of Page Servers.
Failure
A high-traffic site should plan for failure. Even if hardware
and networks never fail, machines must be stopped sometimes for
maintenance.
Provide a backup Dispatcher.
Ensure that all Web libraries are available on at least two
Page Servers, so that no single Page Server failure can stop
access to your data.
Ensure that if any Page Server fails, the remaining Page Servers
with the same Web libraries have sufficient extra capacity to
handle the failed Page Server's load.
If you use a single Web server, keep a hot backup ready.
If possible, plan for your backup Dispatcher and Page Servers
to remain accessible even if your primary network fails.
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IBM eNetwork Communications Server for Windows NT
Host Publisher Feature, Version 6.01