Estimate Memory / CPU / Disk needed¶

This page helps you estimate how much Memory / CPU / Disk the server you install The Littlest JupyterHub on should have. These are just guidelines to help with estimation - your actual needs will vary.

Memory¶

Memory is usually the biggest determinant of server size in most JupyterHub installations. At minimum, your server must have at least 1.5GB of RAM for TLJH to install.

$Recommended\, Memory = (Max\, concurrent\, users \times Max\, mem\, per\, user) + 128MB$

The 128MB is overhead for TLJH and related services. Server Memory Recommended is the amount of Memory (RAM) the server you acquire should have - we recommend erring on the side of ‘more Memory’. The other terms are explained below.

Maximum concurrent users¶

Even if your class has 100 students, most of them will not be using the JupyterHub actively at a single given moment. At 2am on a normal night, maybe you’ll have 10 students using it. At 2am before a final, maybe you’ll have 60 students using it. Maybe you’ll have a lab session with all 100 of your students using it at the same time.

The maximum number of users actively using the JupyterHub at any given time determines how much memory your server will need. You’ll get better at estimating this number over time. We generally recommend between 40-60% of your total class size to start with.

Maximum memory allowed per user¶

Depending on what kind of work your users are doing, they will use different amounts of memory. The easiest way to determine this is to run through a typical user workflow yourself, and measure how much memory is used. You can use Check your memory usage to determine how much memory your user is using.

A good rule of thumb is to take the maximum amount of memory you used during your session, and add 20-40% headroom for users to ‘play around’. This is the maximum amount of memory that should be given to each user.

If users use more than this alloted amount of memory, their notebook kernel will restart.

CPU¶

CPU estimation is more forgiving than Memory estimation. If there isn’t enough CPU for your users, their computation becomes very slow - but does not stop, unlike with RAM.

$Recommended\, CPU = (Max\, concurrent\, users \times Max\, CPU\, usage\, per\, user) + 20\%$

The 20% is overhead for TLJH and related services. This is around 20% of a single modern CPU. This, of course, is just an estimate. We recommend using the same process used to estimate Memory required for estimating CPU required. You cannot use jupyter-resource-usage for this, but you should carry out normal workflow and investigate the CPU usage on the machine.

Disk space¶

Unlike Memory & CPU, disk space is predicated on total number of users, rather than maximum concurrent users.

$Recommended\, Disk\, Size = (Total\, users \times Max\, disk\, usage\, per\, user) + 2GB$