I have a master redis server (S1) and I have 6 other servers. I want them to have local redis slaves, so any change on the redis master will be replicated to the slaves on each local server
Can I write on a slave and make this one update the master, and then the master will update the other slaves?
You can disable read-only mode on a slave, but the writes to the slave will be ephemeral and discarded when the slave resynchronizes or is restarted.
Also this feature will possibly be dropped in the future.
See http://redis.io/topics/replication#read-only-slave