Check out the LimeSurvey source code on GitHub!
Welcome, Guest
Username: Password:

TOPIC: Server question for Limesurvey

Server question for Limesurvey 2 years 10 months ago #100007

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
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?
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 10 months ago #100008

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
One thing I wanted to ask especially: do you think that 512MB of Ram is enough or should this be increased?
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 9 months ago #100474

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
Seems like no one has an answer for this one?
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 9 months ago #100481

  • c_schmitz
  • c_schmitz's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 996
  • Thank you received: 135
  • Karma: 97
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.
Best regards

Carsten Schmitz
LimeSurvey project leader
The administrator has disabled public write access.

Server question for Limesurvey 2 years 9 months ago #100482

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
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...
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 9 months ago #100485

  • c_schmitz
  • c_schmitz's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 996
  • Thank you received: 135
  • Karma: 97
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 :)
Best regards

Carsten Schmitz
LimeSurvey project leader
The administrator has disabled public write access.

Server question for Limesurvey 2 years 9 months ago #100487

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
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!
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108282

  • Gordon55M
  • Gordon55M's Avatar
  • Offline
  • Junior Lime
  • Posts: 29
  • Thank you received: 1
  • Karma: 0
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.
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108287

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
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??
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108295

  • Gordon55M
  • Gordon55M's Avatar
  • Offline
  • Junior Lime
  • Posts: 29
  • Thank you received: 1
  • Karma: 0
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.
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108299

  • holch
  • holch's Avatar
  • Offline
  • LimeSurvey Team
  • Posts: 5062
  • Thank you received: 747
  • Karma: 227
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.
Have a look at the manual! It is a really valuable source for information. Here some helpful links:
Manual (EN) | Question Types | Question Attributes | Workarounds

If you found this answer helpful and it saved you some time please consider a donation to the project to keep Limesurvey going!
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108673

  • rauno_s
  • rauno_s's Avatar
  • Offline
  • Junior Lime
  • Posts: 20
  • Thank you received: 6
  • Karma: 2
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.
The administrator has disabled public write access.

Server question for Limesurvey 2 years 2 months ago #108686

  • Gordon55M
  • Gordon55M's Avatar
  • Offline
  • Junior Lime
  • Posts: 29
  • Thank you received: 1
  • Karma: 0
User rauno_s just gave a great suggestion on another thread regarding server testing. I figure I'd post my results of his suggestion to use Load Impact to test here. I've included charts of each test.

Virtual Specs:
  1. 2 CPU - 4 GB
  2. 4 CPU - 8 GB
  3. 8 CPU - 16 GB

All tests were run using the same survey and having the application click through the survey. Each virtual testing server was hosted in New York via Digital Ocean SSD's using LimeSurvey 2.00+ Build 130802 and having MySQL hosted on the same server. VU’s were distributed equally from Ashburn, Chicago, Dallas, Palo Alto, and Portland. Each VU was using a generic “Load Impact Browser” to simulate this over an unlimited speed network.

Analysis:
CPU usage is the issue in this test, not memory. The 2 CPU’s survey handled about 100 Virtual Users (VU) before both CPU’s hit 100% and stayed there for the remainder of the 5 minute test. The 4 CPU survey test handled 125 VU’s before being strangled at 100% CPU usage for all 4 CPU’s. The 8 CPU run was obviously the best whereas the 8 CPU’s hit 100% 6 times and recovered very quickly (1-2 seconds) back to a 50-75% CPU usage range. 100% all CPU usage hit at 157, 175, 195, 215, 237, and 247 VU’s, but again they quickly recovered. User load time was predominantly under the 10 second window and hovered mostly at around 4 seconds for the 8 CPU virtual. The 2 CPU and 4 CPU virtual surveys were consistently above 10 second page load times once the CPU’s maxed out.

Charts:
2CPU - 4GB RAM


4CPU - 8GB RAM


8CPU - 16GB RAM
The administrator has disabled public write access.
The following user(s) said Thank You: mhkuu
Moderators: ITEd
Time to create page: 0.301 seconds
Imprint                   Data Protection Statement                  Revocation information and revocation form