Problems with architecture

Problems with architecture

by Albert Ramsbottom -
Number of replies: 10

We are migrating up to a 1000 Moodles as part of an infrastructure and version change and as part of this migration we are allowing schools to start again with what we call a fresh new Mini Moodle

Architecture have already specified these new Mini Moodles which will be running on Azure

They are small insofar as they have 1 processor core and 0.75GB of RAM with MySQL running on the same Ubuntu VM.

We have some problems with the DB crashing or just stopping in the middle of the night, during its scheduled dump for its backup.  I kind of know the answer to this but I am asking to get other peoples opinion on this. I believe this size server is not big enough to run Moodle and the MySQl DB on the same box

Opinions on a postcard please


Thanks

Albert


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In reply to Albert Ramsbottom

Re: Problems with architecture

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

0.75GB of RAM??

You're quite right, you do know the answer wink

Ubuntu server requires a minimum of 192MB. The default configuration of MySQL uses about 400MB.  Even a moderate sized course backup can easily consume another 512MB or RAM. You don't have that much. So, at best it'll run in swap and take forever. At worst, the load will go through the roof and it'll all grind to a halt. 

I would suggest 2GB as a rock-bottom minimum if you want to do heavy processing like backups. 

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Paul Verrall -

Tough to say; I think it probably depends on the size of DB and it's configuration. I get by just fine on 1GB of RAM, but I have take some efforts to optimise for my resources.

I use PostgreSQL for my DB, just as a preference and not because it is necessarily better on low resource machine. However it's not causing me any headaches either.

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Chris Fryer -

To my mind you have a couple of options: you either up the grunt on your vms, or you split each Moodle into one web server and one database.

If you have decent configuration management/orchestration tools at your disposal, I would be inclined to go for the latter.  The web server and database are very different workloads.  On the web servers you have lots of processes and/or threads springing into life and dying, and all competing for resources, whereas on the database you have a long-lived monolithic process that wants to use the lion's share of the resources.

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Albert Ramsbottom -

Yes thanks

I was thinking minimum for very small moodle 1.5GB

The backups are not the course backups, these have been disabled, its a dump of the DB, Moodle and Moodledata

Cheers

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

It depends how it's done, but it could still be trying to build a large in-memory data structure that's pushing it over the edge. 

I've seen Moodle running on some very small hardware but you have to be incredibly creative and you'll probably still end up with a single-user install at best. Time is money and memory is relatively cheap so I suspect bumping the ram is the sensible way forward. 

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In reply to Howard Miller

Re: Problems with architecture

by Albert Ramsbottom -

I agree, unfortunately an IT architect who knows very little about Moodle (What he has found here), has already specified the specs and has costed it all.

I have never worked anywhere with any architects that have got the specs right on any application!! It seems mad to give an architect the job for specifying something they know nothing about and then getting experts in to implement solutions that the experts know wont work.

Oh dear

Albert


PS sorry

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Ken Task -
Picture of Particularly helpful Moodlers

Postcard questions: are these mini-Moodles full featured 3.1's and will they be upgraded to -> going forward in time (Moodle doesn't stand still)?

Know the question is about DB issues, but what of Search?  Unoconvert + PDF annotations?

'spirit of sharing', Ken


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In reply to Ken Task

Re: Problems with architecture

by Albert Ramsbottom -

Yes they are mini but full featured in terms of blocks/mods that come with Moodle but adding plugins has been disabled

Max 250 users


Yes they will be upgraded using our CHEF infrastructure, every now and then

Cheers

Alberty

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In reply to Albert Ramsbottom

Re: Problems with architecture

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

You can try deleting all the plugins you don't use. It'll help a bit. You can drastically restrict the number of clients Apache can start and you can reduce the memory footprint of MySQL. It might help... as long as nobody actually wants to *use* the thing. 

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