1. A concurrent transaction subsystem for a journal as a reliable high-speed front end for disk writes, the concurrent transaction subsystem comprising: a processor; a memory; and a module running on the processor, the module configured to: receive a request for a first transaction that includes a request to write data in a first location on the memory; write a first data block corresponding to the first transaction to a journal, the journal stored in persistent storage, and the first data block associated with the first location on the memory and said first data block in a form suitable for being written to the first location on the memory; receive a request for a second transaction that includes a request to write data in the first location on the memory; and determine whether the second transaction includes an order independent operation, wherein an order independent operation is an operation that will yield the same result regardless of the order of operations, and if so, write a first delta element to the journal, wherein the first delta element is representative of a first order independent operation and is associated with the first location on the memory, said first delta element being in an intermediate form and not suitable for directly being written to the first location on the memory.