What is a good strategy for backing up bitcoind's blockchain files (not its wallet file) without having to take (e.g.) a bitcoind that is powering a counterparty-server instance offline?
Copying the blockchain from a running bitcoind may result in a corrupted copy (https://bitcoin.stackexchange.com/a/25260/1660),
To avoid this, is it best to run a separate bitcoind that pulls the blockchain from the first instance (by adding it as its sole network connection using addnode) and periodically stop that then rsync out any changes? Or is there a less circuitous way of getting a coherent blockchain backup from a live bitcoind?