[mikeyk]

We have a variety of Redis machines, some of them are in a consistent hash ring (the ones we're using for caching); some are using modulo-based hashing (the ones where losing data on adding more machines isn't an option), and some are just single-node installs.

[cdelsolar]

How do you handle write replication? I haven't found any good document on how to do this (meaning, if the Redis master goes down, a slave should be promoted to master immediately).

[mikeyk]

You can hypothetically use something like hearbeatd to do it; we run every Redis master with an attached slave and manually failover for now.

For a small team like ours, we prefer solutions that are easy to reason about and get back into a healthy state (it would take one server deploy to point all appservers at new Redis master), rather than fully automated failover and the "fun" split-brain issues that ensue. Of course that may change as we build out our Ops team, etc.