All disks on our cloud form a complex filesystem which is then mounted back on every hardware node so that all nodes see the exact same files. This gives us opportunity to boot virtual machines on any hardware node without having to copy over large disk image files. Moving virtual machines from one node to another is performed without downtime.
The storage backend works by splitting all files into smaller chunks and then storing them (in real time) in 3 copies on 3 different hardware nodes. It makes our storage highly redundant ... we can survive multiple server failures without data loss.
The storage is also very fast as we only use SSD disks.
