FAQ

Riak MDC Replication FAQ

How to estimate the memory requirements for keylist fullsync

A system needs to be able to hold at least 1 partitions worth of keys in memory. It's a bloom filter, so probably more efficient than all keys but the partition keylist is held in memory until it is complete and shipped over. Alternatively, AAE fullsync would not have this requirement.

Can fullsync replication run between clusters having rings of different sizes?

• No

Can realtime replication run between clusters having different n values?

• Yes, but very inefficiently

How can it be determined if backpressure is being applied during replication?

• look at netstat -a output and see if Recv-Q and Send-Q and growing

How can network performance between source + sink be measured

• iperf

Do replicated puts show up in riak-admin status stats?

• yes, here are the rt puts for a single object on a sink with an n_val=3:

vnode_puts : 3
vnode_puts_total : 3

• see also: https://github.com/basho/riak_repl/blob/develop/src/riak_repl_util.erl#L109

Do bucket hooks on the sink fire?

• No, puts on the sink use disable_hooks: https://github.com/basho/riak_repl/blob/develop/src/riak_repl_util.erl#L117

What happens when the same keys are written into both source and sink?

• be extra darn careful about resolving siblings on either side!
• kittens die

How does repl work on EC2?

• meh
• customers should be comfortable and educated with EC2 BEFORE using Riak EE on it
• customers should probably look at this doc first: http://docs.basho.com/riak/latest/ops/tuning/aws/