Mining steem on multiple machines

A lot of people seem to be confused about configuring multiple nodes for parallel mining, so here are some best practices you may find useful.

The basics of steem PoW mining

Your nodes will keep crunching numbers until they find a valid PoW. When a PoW is found, the account associated with the PoW will enter the miner queue and gain the right to generate a block on the chain when it reaches the top of the queue. When it does reach the top of the queue, the witness node for the account will generate a block, the account will receive the mining reward and leave the miner queue.

Miner vs witness

There are two relevant options in the node config:
witness = "your-steem-account-name"
and
miner = ["your-steem-account-name","PrivateWIFKey"]

So here's the deal:
miner defines which account the current node will associate the Proof of Work with.
This is the account that will enter the miner queue when a PoW is found by the node.

witness defines which account the current node will generate blocks for. That is, once the account reaches the top of the miner queue, this node will be responsible for generating the block and thus securing the mining reward.

Now, for any given account, you do NOT want more than 1 node configured as witness. Otherwise, multiple nodes will try to generate a block at the same time and the network may even consider it malicious activity and punish you.

Mining multiple accounts

It's worth noting that once an account finds a PoW and enters the miner queue, that account can not mine until it leaves the miner queue (this currently takes about 2 hours).
For this reason, it's recommended to set up multiple accounts for mining, so even if one of them is in the queue, your nodes can still try to find PoW for the other accounts.

Bottom line

With all that in mind, here's what you wanna do:

Say you have n nodes. Depending on your total hash power, you will want to have at least 3 miner accounts.

On all n nodes:

miner = ["your-account-2","Private-WIF-Key-Of-Account-2"]
miner = ["your-account-1","Private-WIF-Key-Of-Account-1"]
miner = ["your-account-3","Private-WIF-Key-Of-Account-3"]

The accounts will enter the miner queue in alphabetical order of the account names, regardless of the order you define in the config. So in this case, "your-account-1" will enter first, and if you find a PoW while that account is already in the queue, "your-account-2" will enter the queue.

On only 1 (preferably the most stable) node

In addition to the miner entries, have witness lines for all accounts
witness = "your-account-2"
witness = "your-account-1"
witness = "your-account-3"

Hopefully this helps clear up some of the confusion about configuring multiple nodes for steem mining.