[ffk]

Something to consider, if you are IO constrained, compression may speed up reads because you shift some of the cost of IO to the CPU.

Ultimately, you'll need to measure this to know for sure, and those results will likely only be valid on a given hardware configuration.

OverlayFS also has a "copy_up" function, where the file is copied at the initial write. Once the copy is done, I'd expect write access to be fast. Again, you'll need to measure this.

The setup could probably look like:

container read/write -> OverlayFS([mutable fs as overlay] -> [squashfs layer as underlay] -> [squashfs layer as underlay])