Installation

Seeking advice on AWS EC2 specs for server

Seeking advice on AWS EC2 specs for server

by Debbie Yuster -
Number of replies: 7

I'm a longtime WeBWorK user but a first-time (or more accurately, zeroth-time) sysadmin. My college will (hopefully) be funding an AWS EC2 instance to use as a WeBWorK server. I was wondering what you'd suggest for the instance type and size. I would like the server to accommodate 5-10 courses of 20-30 students each. Let's assume that the server will be used only for homework, not for gateway quizzes. Seems 20GB might be a good disk size, but I'm not sure about the rest, and I need to send my desired instance specs to the powers that be.

Thanks,

Debbie

P.S. I'm not confident I'll be able to get an official SSL certificate, so I may need to disable lighttpd, thereby increasing the load on the server.

Tags:
In reply to Debbie Yuster

Re: Seeking advice on AWS EC2 specs for server

by Danny Glin -
The bottleneck for a typical WeBWorK server is usually RAM, so I recommend getting 16GB, though it may be possible to get away with 8GB.  I can't recall ever hearing about people running into problems due to lack of processing power, so two processor cores is probably enough.

In terms of disk space, you can probably manage with 20GB, but you will have to be diligent about cleaning up things like logs and temporary files.  If you can upgrade to a bigger disk without a significant price jump, going to 40 or 50GB will give you more breathing room.
In reply to Danny Glin

Re: Seeking advice on AWS EC2 specs for server

by Arnold Pizer -

Just a note that the AMI is set up so that temporary files are deleted by cron jobs and the timing log is covered by log rotation.  But you should keep an eye on things (e.g. run df every so often). 

In reply to Arnold Pizer

Re: Seeking advice on AWS EC2 specs for server

by Debbie Yuster -

Thanks everyone, I appreciate the advice! But now I'm confused. The wiki page mentions a t2.small (2 GB RAM) or t2.medium (4 GB RAM) as a good starting point. But Danny and L Ng have suggested 8-16GB RAM. Here are the AWS instance specs. Getting 8GB of RAM would require a t2.large and 16GB would require t2.xlarge. But the MAA's own server which hosts 150 active courses is a t2.2xlarge with 32GB RAM. Doesn't that imply that 16GB would be tremendous overkill for my measly 5-10 courses of ~25 students?

I don't mean to argue with those who have alot more expertise than I do, and I recognize that RAM needs may not scale linearly. I'm just trying to figure out the smartest way to balance performance and cost, as I am the sole advocate for my college adopting and paying for a WW server.

Do you think a t2.medium (2 CPU cores, 4GB RAM) would crash under the load or be frustratingly slow, and I should ask for a t2.large? Large is 50% more expensive.

(Disk space seems to be much less of an issue - each additional 10GB of drive space looks to cost an additional $~1/month).

Thanks,

Debbie

In reply to Debbie Yuster

Re: Seeking advice on AWS EC2 specs for server

by Alex Jordan -
Based on my experience with DigitalOcean (a competitor to AWS) a t2.medium would be adequate. It has 2 CPUs and 4 GB of RAM, which is the same as what Runestone hosting was using when it only had about a dozen concurrent courses. So maybe you could get away with less, but that looks sufficient from my limited experience.

Again, I don't have AWS experience, but DigitalOcean made it nearly trivial to change these things when the need arose. If that is the case with AWS, you could start small. If/when things run slow, first start playing with the apache settings MaxRequestWorkers and MaxConnectionsPerChild. But if that doesn't help, next step is upgrading, assuming AWS makes that easy.
In reply to Alex Jordan

Re: Seeking advice on AWS EC2 specs for server

by Debbie Yuster -

Thanks Alex and Arnie for the follow-ups. I will ask for a t4g.medium (2 cores, 4GB RAM) but let the powers that be know there's a chance I'll need to move up. Moving up does look easy on AWS - I'd just have to update my stable URL to point to the new IP address.

In reply to Debbie Yuster

Re: Seeking advice on AWS EC2 specs for server

by L Ng -
For our production, we plan to use AWS as well. As AWS is "elastic" I wouldn't worry too much about as like VMWare, they can easily handle compute resources when needed.

16 GB and about 200 GB is a good start for me.