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===How do you define "concurrent users"?===
As has been repeatedly stressed in the [http://moodle.org/mod/forum/view.php?f=94 Hardware and performance] fourm, the load on the server depends primarily on the number of concurrent users, not on the total number of users neither the number of users logged-in at a given time. In this context, the concurrent users are those for whom the server actively doing something (see Wikipedia [http://en.wikipedia.org/wiki/Concurrency_(computer_science) Concurrency]). It may by processing a webpage written in PHP, querrying the database or simply transfering a file.

===How do I benchmark a Moodle-site?===
You can of course benchmark each component of the software stack: operating system, webserver, database server, PHP (see [[Performance#Obtain_a_baseline_benchmark]]). But there is no easy formula to deduct the maximum number of concurrent users from those results.

There is a PHP-script, the [http://moodle.org/mod/forum/discuss.php?d=57028 Performance perspectives - a little script], circulating amoung the Moodle-community which calculates a ballpark figure. The current version is attached to the [http://moodle.org/mod/forum/discuss.php?d=57028#p296907 posting on 1. March 2007].

Warning: Note that running this script on a production server may have unwanted side-effects. You are strongly adviced to run it on a test-site.

===What are PHP-accelerators?===
See Wikipedia article [http://en.wikipedia.org/wiki/PHP_accelerator PHP accelerator].

Available software are documented [[Performance#PHP_performance]].

===How do I cluster Moodle?===

See [[Performance#Scalability]]

===How do I replicate Moodle?===



===My site is very slow, what should I do?===

First find out "how slow". (The theme-trick here).

The next question is, whether the performance is normal or something malfunctions. There are many things which can malfunction:
* hardware
* crashed filesystems, specially network filesystems
* memory leaks or other crashes in the system
* bug in Moodle
* corrupted database

Or your performance could be "normal" under the given circumstances:
* Is it a root-server, dedicated server, virtual (shared) server
* How much RAM, processing power do you have?
* What is the software stack you use? (Unix or Windows, Apache or IIS, MySQL, PostgreSQL or SQL-Server, ...?)
* how many concurrent users slows the system down
* what modules/activities they use? Check [[Performance#Performance of different Moodle modules]]
* is your networt setup property? DNS, firewalls. Also check local firewalls and other local security tools?

[[Performance#Obtain a baseline benchmark]] and compare it with the published figures.

See also: 
* [http://moodle.org/mod/forum/discuss.php?d=102978 1000 concurrent users]
* [http://moodle.org/mod/forum/discuss.php?d=103040 Tool to estimate server's maximum concurrent users]

===What are the requirements for N users?===

[http://moodle.org/mod/forum/discuss.php?d=111847 A moodle setup for 10K simultaneous users]

===How many users will my installation support?===

This is another way of asking the same question as above. Please move up.

===Which operating system is the best?===

===What is the best webserver?===

===Should I go for 64 bit or is 32 bit OK?===

===What hosting provider do you recommend?===
http://moodle.org/mod/forum/discuss.php?d=99405

[[Category:FAQ]] I [[Category: Administrator]] I [[Category:Performance]]