US Patent 7613890 Consistent replication across multiple storage devices

Concurrently replicating a plurality of storage devices includes disabling writes to all of the storage devices, setting a pending state change indicator for all of the storage devices after disabling writes without altering a replication state of any of the storage devices, and enabling writes to the storage devices after setting the pending state change indicator. An I/O operation to a particular one of the storage devices having a set pending state change indicator may cause the replication state of the particular one of the storage devices to change to provide for replication. Concurrently replicating a plurality of storage devices may include, following changing the replication state of the particular one of the storage devices, clearing the pending state change indicator.