Tmp storage and small volumes


I’m trying to understand if there’s any ephemeral filesystem storage available to apps. I only need a couple hundred megabytes and it’s okay if I lose it. I’ve seen via search here that maybe apps have access to up to 8GB and I’ve also read that /tmp is mounted as a RAM disk so would actually consume memory if written to.

What’s the full story with regards to the filesystem an app has access to?

Additionally, is it possible to provision and attach persistent storage volumes of less than 1GB to an app?

Also what happens to a volume when there are multiple instances of an app in a single region. Do they all share the volume or is there one volume per instance?

The root partition is available to your apps upto 8G per VM. The entirety of it is pseudo tmpfs (or more aptly, a cache dir) in the sense that if the VM goes, as does the data on it (which is what you’re looking for, anyway).

3G is the default. And, I’d wager you cannot go lower than 1G.

Cool that makes sense. I assume then writes to the tmpfs / cache dir doesn’t count towards whatever memory I have available on the vm then?

If /tmp is actually tmpfs, you don’t really want to be storing large blobs in it on a VM with limited RAM and no swap. On my Fly apps (running alpine images as base), /tmp isn’t mounted as tmpfs. It is simply a dir in / (root) which is the partition /dev/vdb mounted with ext4.