Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for storing data reliably across groups of storage nodes. In one aspect, a method includes receiving (n−f) data chunks for storage across n groups of storage nodes and generating (f−1) error-correcting code chunks using an error-correcting code and the (n−f) data chunks. The (n−f) data chunks are stored at a first group of storage nodes. Each data chunk of the (n−f) data chunks is stored at a respective second group of storage nodes. Each code chunk of the (f−1) code chunks is stored at a respective third group of storage nodes. Each second group of storage nodes and each third group of storage nodes is distinct from each other and from the first group of storage nodes.