Durable storage – without disks?

A deep dive into how Sprites (hardware-isolated stateful sandboxes) achieve durable storage without physical disks. Starting from Linux file system basics, it explains how file systems like ext4 interact with block devices via BIO requests, how OverlayFS enables layered container file systems, and how the Network Block Device (NBD) protocol allows block IO to be handled by a user-space process instead of hardware. Sprites use this to run a process called SpriteFS that intercepts block-level reads/writes and stores data as chunks in object storage, with metadata in a SQLite database also synced to object storage — making sandboxes both disposable and persistent.