Patent ID: 7519859

Claim:
A method comprising: receiving a write transaction by a primary device; transmitting the write transaction from the primary device to N backup devices, where N is greater than one; by each backup device, recording the write transaction to a local redo log stored at a high-performance storage; transmitting a notification to the primary device that the write transaction has been recorded; after the primary device has received notifications from M of the N backup devices, where M is less than N, committing the write transaction by the primary device; after committing the write transaction by the primary device, recording the write transaction by the primary device to a low-performance storage, such that the write transaction is recorded by the primary device to the low-performance storage after the M of the N backup devices have each recorded the write transaction to the local redo log stored at the high-performance storage, wherein the low-performance storage has a lower performance than a performance of each high-performance storage; and, in response to the primary device incurring a fault, one of the N backup devices becoming a new primary device, such that remaining of the N backup devices are N−1 backup devices; the new primary device determining which of the N backup devices has a newest local redo log; where the backup device having the newest local redo log is one of the N−1 backup devices, the new primary device requesting the backup device having the newest local redo log to send the newest local redo log to all other of the N backup devices; where the backup device having the newest local redo log is the new primary device, the new primary device sending the newest local redo log to the N−1 backup devices; by each of the N backup devices except the backup device having the newest local redo log, receiving the newest local redo log from the backup device having the newest local redo log; updating the local redo log to a same state as the newest local redo log received.