Geschwindigkeit FAQ

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Was ist mit gleichzeitige Nutzer/innen gemeint?

As has been repeatedly stressed in the Hardware and performance forum, the load on the server at a particular time depends on the number of concurrent users. Not on the total number of user accounts and not on the number of users logged-in. The term "concurrent users" is used to mean those users for whom the server is actively doing something . It may by processing a webpage written in PHP, querying the database or simply transferring a file. (see also Wikipedia Concurrency). Strictly speaking we mean the number of active web server processes (each of which consume memory) and also the number of database connections.

Warum ist gleichzeitige Nutzer/innen kein geeignetes Maß für Geschwindigkeitsabschätzungen?

When considering a new site or new hardware, this metric is not very useful because you have no idea how many 'concurrent users' (a better term might be 'concurrent requests') you will have.

For example, if you have 10,000 registered users and you estimate that, during times of peak load, about 1,000 of those users will be using the system, there is no easy way to obtain the number of 'concurrent users'.

It depends on what the users are doing (if they are contributing to a forum they will make fairly frequent requests but with long pauses to write posts; if they are downloading a PDF they will only make a single request but it will take a long time; if they are doing a quiz they will make very frequent requests).

It also depends on system performance. If your system can serve a typical page in 0.1 seconds then if you have 10 people making a request within a second this is an average of 1 concurrent user. If your system takes 1 second to serve a page then the same usage pattern results in an average of 10 concurrent users.

In addition, the number of concurrent users is not a very accurate measure of demand because a "concurrent user" may be downloading a large file, which takes time to transfer based on the speed of their network connection. While this does place a demand on the server, a server may well be able to cope easily with sending out 10 large PDF files to 10 concurrent users with slow network connections, whereas it might struggle if 10 users were continuously making separate PHP requests to a complex page such as quiz.

Was ist ein geeignetes Maß für Geschwindigkeitsabschätzungen?

Peak requests per second (either from web logs, mdl_log lines, or similar) is probably a better way to roughly estimate demand on the server - but it is still very difficult to work this out for a new server with unknown usage patterns.

Welche Hardware benötige ich für N gelichzeitige Nutzer/innen?

Firstly see above to make sure you express 'n' somewhere near correctly. Unfortunately, the answer is "it depends". It will depend primarily on your chosen operating system, your software configuration (especially web server and database tuning) and what the users will be doing. The worst possible scenario is a large class all starting a timed quiz at exactly the same time. Luckily, users sat reading stuff are not generating any server load at all (until they click for the next activity/page). Very roughly, worst case, your Moodle site may only handle as few as 10-20 concurrent users per GB of memory. Moodle is a large application and can easily use more that 50MB (sometimes a lot more) of RAM per process. If you are planning a very large site, you are strongly encouraged to run a pilot first and take some measurements or resources used.

Prospective Moodle users tend to vastly over-estimate the required concurrency. It's potentially a very expensive mistake if you get this wrong.

Was ist der einfachste Weg, die Geschwindigkeit zu verbessern?

Mehr Soeicher kaufen!

Wie kann ich einen Benchmark für eine Moodle-Site durchführen?

You can of course benchmark parts of the system separately: the hardware as seen by the operating system (eg. CPU, disk access), web server performance, database server performance, execution on PHP operations, etc. For further details see Performance_recommendations#Obtain_a_baseline_benchmark.

But there is no easy formula to deduce the maximum number of concurrent users from those results. There is a PHP-script, the Performance perspectives - a little script, circulating amoung the Moodle-community which calculates a ballpark figure. The current version is attached to posting on 25. March 2011.

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.

Was sind PHP-Acceleratoren?

See Wikipedia PHP accelerator.

Available software are documented under Performance_recommendations#PHP_performance.

You find some user suggestions here Update on PHP-accelerators.

Wie setze ich Moodle als Cluster auf?

See Performance_recommendations#Scalability

Wie vervielfältige ich Moodle?

Mirroring_Moodle

How to Replicate MOODLE ??!!

Mein Moodle ist sehr langsam, was kann ich tun?

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
networking issues (DNS, firewalls, ...)

Or your performance could be "normal" under the given circumstances:

Are you on a dedicated server or a shared (virtual) 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 can you support
what modules/activities you use? Check Performance_recommendations#Performance of different Moodle modules

Performance_recommendations#Obtain a baseline benchmark and compare it with the published figures.

Was sind die Server-Anforderungen für N Nutzer/innen?

A moodle setup for 10K simultaneous users

Wie viele Nutzer/innen unterstützt meine Installation?

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

Was ist der beste Webserver?

It depends who you ask. Apache is almost universal on Unix and Linux. IIS is native to Windows Server but Apache can be used as well. As always, the latest version available is likely to provide the best performance. There are other "niche" web servers. If you are interested in one of those you are likely to know about it already.

Soll ich einen 64-Bit-Server verwenden oder reicht ein 32-Bit-Server?

Die meisten Server heutzutage sind ohnehin 64-Bit-Server. Bei Desktop-Installationen: Wenn Sie die Wahl haben, sind 32-Bit-Systeme wahrscheimlich besser unterstützt.

Welchen Hosting-Provider empfehlen Sie?

Die Moodle-Partner sind vom Moodle Headquarter geprüft, sie verfügen über eine umfassende Moodle-Expertise und können umfangreichen Support anbieten. Sie bieten jedoch nicht immer die billigste Lösung, wenn Ihr Budget knapp bemessen ist (fragen Sie trotzdem nach!). Bei preiswertem "Shared Hosting" kann es passieren, dass nicht genügend Kapazitäten für Moodle bereitgestellt werden. Es gibt ganz verschiedene Möglichkeiten, und es hängt ganz wesentlich von Ihren Anforderungen ab. Siehe auch dieser Diskussionsbeitrag.

Siehe auch

Diskussionsbeiträge im Kurs Using Moodle auf moodle.org:

Documentation