Storage requirement on devices for CHT

How much storage should users have available on their devices to run CHT without issues? 100MB free on disk? 500MB free on disk?

At what point should a program person intervene and help the CHW free some disk space?


As a starting point, our docs say that 8GB is required.

This of course will be partially filled up with the Android OS, so I’ll let others with more field experience weigh in with a more nuanced answer.

So 8GB is recommendation for total disk. But once users start using the phone (WhatsApp, camera, etc) and the disk starts filling up: when should program staff intervene to ensure the app stays healthy?

We need to avoid storage pressure eviction and QuotaExceeded exceptions.

This is what ChatGPT says:

The exact threshold at which storage pressure eviction is triggered may vary depending on the operating system and version of Chrome being used, as well as the available storage space on the system. However, in general, Chrome is designed to monitor the available storage space and automatically trigger storage pressure eviction when necessary to help ensure the browser doesn’t use up too much space on the system.

In the first iteration to monitor this, I’m going to arbitrarily start with a 250MB limit and if there is good reason/evidence to increase we can bump it up.

Unfortunately this is a complicated issue and I haven’t managed to find a clear answer, and it depends on the OS type and version, browser and version, available space, total space, and so on.

Another complication is data persistence which the CHT requests at startup but again different browsers are free to choose their own logic for whether or not this is granted. Chrome uses a few metrics to decide whether the user frequently visits the site and then silently grants it. The CHT logs whether this was granted to the browser console (aside: this might be a useful addition to device telemetry?). If data persistence is granted then the browser guarantees data will never be cleared unless the user specifically requests it.

However as CHWs use the device to create or sync new docs, generate tasks, or update indexes at some point the CHT will hit a threshold and not be able to use any more space. Google has stated that for any one app this limit is 60% of the total disk, however this will be lower if other apps or the OS have also be granted some kind of data persistence guarantee…

Medic has done some synthetic testing of these scenarios which may be helpful here.

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