Size of ram ?

danmcguire

What difference does the amount of Ram on a Raspberry Pi 4B make (not that any of them seem to be available?)

Nicolas

Not much difference for a MoodleBox usage only. 2 MB RAM is largely enough for a Moodle server.

Ratna

Nicolas, sweet and short!

danmcguire, your question was also curt and leaves room for interpretation.

First interpretation: When a user navigates the Moodle, will the (average) response time different (gets shorter) along RPi 4B 2G, 4G and 8G models?

This is what Nicolas answered. No, it won't. Because the RAM is not the bottleneck.

Second interpretation: If 10 users request a page from (click on) Moodle at the same millisecond, will their average response time different (gets shorter) along RPi 4B 2G, 4G and 8G? Same question for 20, 50, 100, ... users?

I haven't measured, but expect the response times to get shorter if these responses come from the (cabled) Ethernet LAN - assuming a quality router and network cabling, means an error-free 1 Gbit/s link to the router. I expect a less rosy picture if those devices are connected to the wi-fi of the access point of MoodleBox. Wi-fi is a shared medium with much more collisions than (cabled) Ethernet. And the experiment will stop any way when you pass 20 devices.

danmcguire

Thanks, Nicolas.

Nicolas

Ratna I haven't measured, but expect the response times to get shorter if these responses come from the (cabled) Ethernet LAN - assuming a quality router and network cabling, means an error-free 1 Gbit/s link to the router.

Agreed.

I've made measurements with a RPi 3B+ (1 MB RAM) a few years ago and could not see any performance drop with 200 ethernet concurrent users. This tends to show that RAM is not the bottleneck anyway.

Ratna

Nicolas That is massively good news. I too did this years ago and wondered why the score doesn't change much even amoung RPi 3 A+, 3 B, 3 B+ and 4 B 4 GB: http://www.syndrega.ch/blog/ > Benchmarking MoodleBox on different Raspberry Pi models. The OP is interested in comparing RPi 4 B 2 GB, 4 GB and 8 GB. I can't do a side-by-side comparison of these models since I have only a RPi 4 B.

I am interested in your measurements. Were those 200 "ethernet concurrent users" real users? If so, what were they doing? What was the "concurrency" exactly? Number of active users during the last 5 minutes, for example? Or did you simulate them? With https://docs.moodle.org/dev/Load_testing_Moodle_with_JMeter, by any chance?

Nicolas

Ratna Were those 200 "ethernet concurrent users" real users?

No. I used Apache Bench to simulate around 200 users. Apache Bench works by sending simultaneous requests to the web server during a few minutes. This is absolutely not a sensible measure of Moodle usage with 200 simultaneous users, which is a total different thing.

I tested MoodleBox with JMeter to simulate Moodle usage, and it was quite good (also a few years ago, on RPi 3B).

Anyway, MoodleBox is not implemented to support big cohorts of users.

Ratna

Nicolas

How big is too big for the (Ethernet side of a) MoodleBox is the question. People generally have the feeling that a "server" needs to be big and as a result run servers (24/7) unnecessarily, wasting energy, when the whole world is running deeper and deeper in to an environmental crisis. Need to produce some numbers. In the meantime, if you find any related links on RPi as a LEMP stack or better as a Moodle server, please do post them here.

danmcguire

Thank you for your insightful comments, Ratna and Nicolas. I was asking primarily to know what the difference would be in case one or another of the Raspberry Pi's became available. All of your comments make sense and help me be more informed. Thank you

Ratna

danmcguire

Please notice that we were answering the original question, "What difference does the amount of Ram on a Raspberry Pi 4B make", whereas you wanted "primarily to know what the difference would be in case one or another of the Raspberry Pi's became available" - i.e. any RPi capable of running MoodleBox, which are Zero 2 W, 3A+, 3B, 3B+, 4B and 400. That is a different question. Glad that the information helped nevertheless.