1. A distributed storage system configured to implement a selective read-only mode, comprising: a plurality of storage modules configured to communicate via a network, each of the plurality of storage modules comprising at least one processor and configured to process at least one of read and write requests on behalf of the entire distributed storage system, wherein the storage modules configured to handle write requests are configured to individually enter a read-only mode if at least one condition is detected that affects persistent storage on a respective storage module; and an allocation module configured to exclude storage modules operating in read-only mode from processing write requests.