A bit unorthodox, I normally just write about MySQL Cluster here, but I just wanted to understand how much latency semi-sync replication adds.

The test was very simple:

• two mysql servers, interconnected (same switch) on a 1 Gig-E network
• one table (see below)
• comparing insert performance (one thread) with 'no replication at all' and 'semi sync replication enabled'.
  
• bencher (had to hack it a bit to make it work with vanilla mysql) running one thread, inserting 4B+128B+4B = 136B of data

CREATE TABLE `t1` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`data` varchar(255) DEFAULT NULL,
`ts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
KEY `ts` (`ts`)
) ENGINE=InnoDB 

Test 1 - no replication

src/bencher -t1 -r 30   -q "insert into t1(b) …