Moodle in English: Dual server setup: More powerful server as webserver or database server ?

Dual server setup: More powerful server as webserver or database server ?

by Michele Balazs - Thursday, February 24, 2005, 7:00 PM

Hiya,

I have two servers. one a dp 3200 MHz with 4GB RAM and the other 930 MHZ with 2GB RAM. I am intending to set up one as a database server and the other a webserver. My question is should the more powerful server be the database server or webserver ?

Thanx

Mich

Re: Dual server setup: More powerful server as webserver or database server ?

by Genner Cerna - Thursday, February 24, 2005, 7:25 PM

The webserver should be the powerful, cause php consume more memory.

Maybe you could implement clustering for much better setup.

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Re: Dual server setup: More powerful server as webserver or database server ?

by Michele Balazs - Thursday, February 24, 2005, 8:35 PM

Thanx for your reply Genner. I did consider clustering , but I wonder how difficult it would be to set up.

Mich

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Re: Dual server setup: More powerful server as webserver or database server ?

by Michael Penney - Friday, February 25, 2005, 2:13 AM

I'd actualy use the more powerful one as the db server.

It's easier to add new apache/php servers either as a load balanced cluster or as round robin than it is to add more db servers, so a general midrange multiserver set up has the most powerful cpu doing the database and then one or more lower end cpus doing php/apache.

See Martin Langhoff's pdf in the Moodle Enterprise discussion for a great example of a mid-range (30k students) cluster (http://catalyst.net.nz/moodle/enterprise).

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Re: Dual server setup: More powerful server as webserver or database server ?

by Martín Langhoff - Friday, February 25, 2005, 7:43 AM

I agree with both Michael and Genner

If you know you'll only use 2 servers, put the strongest as the webserver -- Moodle uses more CPU cycles and memory there. On the other hand, if you want to prepare for "transparent" growth, have everything ready for a cluster, with the strongest server as the DB server.

One thing that is important: the webservers want a lot of RAM; not necessarily the fastest CPU, but a lot of RAM. If you have many users on dial-up or other slow connections, a reverse-proxy in front helps heaps too.

By the way, it's odd to hear 30K students classified as mid-range. How many students have you got, Michael

? I don't really worry, that cluster will be growing in usage, to (I think) ~90K users towards the end of 2005. We'll be learning *more* about Moodle scalability, and I may earn a "top-range" label for the cluster

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Re: Dual server setup: More powerful server as webserver or database server ?

by Michael Penney - Saturday, February 26, 2005, 12:48 AM

Hi Martin, Cal State has 409,000 students surprise

.

Individual campusses range from ~7000 to ~30,000. Some classes range near to 1000 students at the larger CSUs. The 25-35k student campusses are burning their BB/WebCT servers up. BB doesn't seem to be very cluster friendly, WebCT CE doesn't do it at all, but I have no idea how WebCT vista will scale up.

Your work is highly appreciated, by the way. Scalability is something that comes up frequently among the CIOs--if we don't even have "application servers" how can Moodle be scalable?

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Re: Dual server setup: More powerful server as webserver or database server ?

by Bob Boufford - Saturday, February 26, 2005, 2:21 AM

Michael,

WebCT Vista does quite well in a clusted environment. We have courses with upwards of 2000 students and one with 5000 students. Institution is 40k along with hosting of additional institutions so upwards of 60k students.

Cheers,

Bob

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Re: Dual server setup: More powerful server as webserver or database server ?

by Martín Langhoff - Saturday, February 26, 2005, 10:07 AM

Wow! That's a lot of students! And are you running Moodle with all/some of them? Have you got stats of what percentage of them have accounts in your Moodle setup, and how many actively use it?

I'm surprised at WebCT/BB doing badly with >35K users. Any idea why?

(*blush*, thanks! I must confess, I am only one of a team. Penny has done a lot to make this scalability stuff happen, and Andrew McMillan (Postgres guru) and Richard Wyles (project champion/PM/NZVLE). At the pace Richard's leading us, all of NZ will be on Moodle by 1.6!)

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Re: Dual server setup: More powerful server as webserver or database server ?

by Michael Penney - Saturday, February 26, 2005, 11:17 AM

No, not nearly all of them we're mostly running Blackboard Enterprise/WebCT CE here, one install at each campus, a central CSU Moodle server is only in the very very early discussion stages. Folks here worry that a simple little PHP app. would have more problems than the serverside java/JSP/MSSQL/apache/IIS/ (Blackboard Enterprise runs all of them at the same time) frankensteins, so your pioneering work helps (bigtime) to make the case.

From Bob's post, WebCT Vista fixes the scalability problems that CE has, for only $150,000/year surprise

(do they charge more for clusters than single servers?), I'm not sure what BB's next move is, they seem to have some pretty serious engineering issues to overcome to scale affordably.

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Re: Dual server setup: More powerful server as webserver or database server ?

by Martín Langhoff - Saturday, February 26, 2005, 12:00 PM

I wouldn't want to be trying to make BB Enterprise be scalable or stable after what you've told me. Sysadmins must *love* it

I'll keep people posted as we grow in usage on our server. This week a few thousand new users start courses on the cluster, we'll see if the load starts to show up in the graphs -- so far it's barely a blip.

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Dual server setup: More powerful server as webserver or database server ?