A method is provided for increasing data storage reliability in a heterogeneous storage system including multiple storage devices of different types. The devices store respective data subsets of a dataset. The method includes accessing configuration parameters for the dataset including first and second amounts of the data subsets respectively stored on the multiple storage devices. The method further includes estimating an initial global reliability of the heterogeneous storage system for the dataset, based on the configuration parameters. The method also includes determining an increased global reliability of the storage system for the dataset, by estimating a global reliability as would be obtained by modifying at least some of the configuration parameters, whereby at least the first and second amounts of the data subsets respectively stored on the devices are modified. The method further includes reconfiguring the dataset stored across the heterogeneous storage system according to the modified configuration parameters.