Hi everyone!

I am currently hosting my surveys on a VPS with the following specifications:

• 1024MB Ram
• 50GB HDD

However, on this same VPS I am also running some other applications like a download center for files for my clients to download. I fear that a client downloading big files could have an impact on the survey performance, which is why I would like to move either the download center away, or the Limesurvey. At the moment I am looking into the option to move Limesurvey to a separate VPS with SSD instead of HDD, because I have read that SSDs are a lot quicker when the application requires a lot of MySQL and I figured that this is the case for Limesurvey and not so much for the download center.

Do you think it is a good move? I am currently thinking of a VPS with 512MB Ram and a 20GB SSD only for the Limesurvey installation. My surveys usually aren't huge, but this could change over time of course.

Any hint on the size of the VPS and the minimum requirements to run normal surveys save would be great. I know that it not only depends on Ram and HDD, there are of course other factors that have an influence on the quality. But I try to get an idea here. Once I have deployed the VPS I will have to do further tests.

Has anyone experience with DigitalOcean ( www.digitalocean.com/ ) and Limesurvey?

One thing I wanted to ask especially: do you think that 512MB of Ram is enough or should this be increased?

Seems like no one has an answer for this one?

Well, as long as you have a VPS and not a machine of your own it is all guessing here. But SSD is definitely a good idea if data security is given. Is memory enough? Yes, usually does the trick - also depends how much load you are really expecting. Giving LimeSurvey a separate server is always a good idea.

Hi Carsten!

Thanks for the response. Of course a VPS isn't as good as a server, but with guaranteed resources it should be quite fine already.

I don't think I'll have huge loads any time soon. Maximum survey size is usually n=1000, so this should be controllable.

A own dedicated server would be a dream, but on the other hand, at the moment I think it would be a overkill. But a own VPS instance is something that is feasible at the moment. This is why I was thinking about this. Because there will be no impact of other activities on the surveys.

Now I just have to figure out on how to redirect a subdomain to one server and the other subdomain to the other server...

holch wrote: Hi Carsten!
Now I just have to figure out on how to redirect a subdomain to one server and the other subdomain to the other server...

A simple 'A' entry in your DNS configuration of your domain provider pointing to the IP address of the new server should do the trick

Yeah, problem is that my domain provider is the Brazilian "Denic" and I am not sure if they offer this. Not sure if they allow this directly with them. At the moment the subdomains are made via my current VPS.

Well, I'll look into this. Thank you for your help!

Just to add my two cents as I just got destroyed on a VPS with too many concurrent users.

I had a single CPU with 2 GB RAM running 4 separate survey's. The CPU and RAM both maxed out at 100% with 150-200 users at the same exact time causing errors for respondents. Image attached as serverload_old.jpg




I migrated each individual survey to it's own VPS with 2 CPUs and 4 GB RAM, and each are sitting at about 1-50% usage without issue. Image attached as serverload_new.jpg




These were/are all on Ubuntu 12.04.4 x64 SSDs with MySQL DB.

Thanks for your feedback. 150-200 concurrent users are A LOT. With the normal sample sizes of about n=1000 in market research, you would fill the sample in a few hours.

What kind of surveys are you running there and how to you recruit them??

This is being used for program evaluations, so many people are opted in and regretfully all received the invite at the same time (I was unaware of this at launch). The 2 CPU/4GB/SSD server was handling about 600 respondents an hour at the peak.

Moral of the story, throttle invites.

Yes, definitely. Don't send out the emails to all at once, if you have a long list. This kills any survey software. Because chances are high that everyone wants to see what it is about and there you go.

We usually split things up as well, even for smaller surveys.

As said previously - concurrency is what kills. You can bring even a very decent VPS down with high concurrency when at the same time a very modest VPS can host huge surveys with low simultaneous traffic. Throttling invitations is always a good idea.