Self-describing data blocks of a minimum atomic write size may be stored for a data store. Data may be received for storage in a data block at a persistent storage device. Metadata may be generated for the data that includes an error detection code which is generated for the data and the metadata together. An individual atomic write operation may write together the data and the metadata in the data block. When accessed, the error detection code is applicable to detect errors and the metadata may also be applicable to determine whether the data is stored for a currently assigned purpose or a previously assigned purpose of the data block.