JATOS server for my university

Silke

Hi there,

I have been attending the excellent workshop this week and am now talking to the IT team in my department (Psychology, University of York, UK) about setting up a JATOS server. They came back with a few questions that I couldn't answer with 100% certainty, can you please help me?

1. Are experiments run live on the JATOS server or are they downloaded and run on a local machine?
2. How much data will have to be stored and backed up? (For this I know, that will depend on the type of stimuli (e.g audio files..etc). But it'd be good to have some estimates about what would be a good size for a small experimental psychology research group (let's say 5 researchers using only visual stimuli) and what would be a good size for an active Psychology department (let's say 50 active researchers using the whole range) - so I am looking for some sort of lower and upper guestimate here)

Thanks!

kri

Hi Silke,

The first question is easy to answer: JATOS experiments run in the browser and are like any other webpage not downloaded.

The second question is more complex.

For a small research group like you describe with small experiments a server with 2 GB memory might be enough but with 4 GB you are on the save side. For an institute-wide server 4 to 8 GB.

Disk size is really up to you and your experiments: I'd say 20 GB is the absolute minimum and then there is no upper limit, but 1, 2, 4 TB for a institute-wide server are good starting points.

Also I will copy-paste a text that I recently wrote to answer a similar question. It also describes memory and CPU requirements and gives two examples.

-----------------------------

Disk size is mostly determined by the experiments the users are running on this JATOS server and is difficult to predict. In general if an experiment uses or produces video, audio, or large image files the disk size can get very high. On the contrary if an experiment just produces result data in text format, disk size tends to be low.

Memory: Absolute minimum is 1GB - anything else depends on your users and more importantly how many experiments your users intend to run in parallel. Feasible numbers are 1GB, 2GB, 4GB or 8GB.

CPU: not important to my experience - even with a single virtual CPU seldom over 10%

Database

Although JATOS can run with its embedded database for a 'professional' setup a MySQL database is recommended. It can be on the same machine as JATOS is running or an extra machine. It is not necessary to set up tables etc - except for a user and the database itself all setup is done by JATOS automatically.

The database size, like the disk size, depends mostly on the experiments the users are running on the JATOS instance. Importantly, large files (video, audio, images) are usually stored in the file system and not in the database. That makes the database size requirements more predictable.

Backup

Best is to tell your JATOS users to 'export' their result data regularly themselves - the less they will ask you.

A full JATOS backup consists of three directories in the file system and a MySQL dump. It can be done while JATOS is running (only if MySQL is used - not with the embedded database).

Three Examples

cortex.jatos.org

• Intention: JATOS try-out server that is reset every day

• Cloud machine (Digital Ocean) with 1 GB memory, 1 (virtual) CPU, 20 GB disk
• Uses JATOS dockerized with embedded database
• Uses reverse proxy (Traefik) to add encryption
• No backup

experiments.jatos.org

• Intention: free JATOS server during COVID-19 for researchers worldwide
• Cloud machine (Digital Ocean) with 4 GB memory, 2 (virtual) CPUs, currently 80 GB disk (might need more)
• Uses plain JATOS (no Docker)
• Uses MySQL database (no Docker) on the same instance
• Uses reverse proxy (Nginx) to add encryption
• Weekly backups (full disk, with history, managed by Digital Ocean)

In our university

• Intention: JATOS for a single research group
• Virtual machine on a dedicated server, local at the university
• 4 GB memory, 4 (virtual) CPUs, 100 GB disk
• Uses plain JATOS (no Docker)
• Uses MySQL database (no Docker) on the same instance
• Daily backup (whole server, no history)

More about JATOS installation

• http://www.jatos.org/JATOS-on-a-server.html
• http://www.jatos.org/Configure-JATOS-on-a-Server.html

Silke

Great, thanks!