In one aspect, IO recovery mechanisms in active/active replication for storage clusters provide, for each write IO request: determining an extent of pages to be modified; acquiring a lock by a cluster local to the request and locally persisting data; atomically creating an entry in a local journal; and sending, by the local cluster, a data write request to a peer cluster. Upon receiving acknowledgement from the peer cluster of successful transmission, the replication journal entry is cleared, the extent is unlocked, and a notification is returned to the peer. In response to a failure event at the peer cluster after persisting the data at the local cluster and creating the journal entry at the local cluster, an aspect includes sending, to the peer cluster upon recovery of the peer cluster, the journal entry with respect to an extent corresponding to a time of the failure event.