Faster disks, shared fairly
A sandbox's disk no longer has a fixed speed or a burst to run out. It shares its server's drives with the sandboxes beside it, in proportion: at least about 40 MB/s each way, and up to about 1 GB/s when its neighbours are quiet. A busy neighbour slows your writes a little rather than stalling them, and a pause stays quick on a busy server. See the sandbox environment.