![]() > A stretched 3-data center cluster architecture involves three data centers that are connected by a low latency (sub-100ms) and stable (very tight p99s) network, usually a “dark fiber” network that is owned or leased privately by the company.ġ00ms would theoretically be enough to span the contiguous United States, but the references to "very tight p99s" and "dark fiber" make me wonder if 100ms is actually acceptable, or just a theoretical maximum that can only be allowed under absolutely perfect conditions. My understanding is that it’s generally a bad idea in Kafka due to the latency, but I could be wrong.ĭefinitely sounds like there are some tight latency requirements: I was talking about different regions altogether, not just different AZs. It's not obvious to me if this scenario is plausible or not. if the load is overwhelmingly eventually consistent read operations and their multi-hop topology with proxies doesn't sufficiently reduce the load on the replicas. Then you have this server that helps handle the load but doesn't increase the number of servers that have to participate in a round. If 7 aren't enough.I'd probably rethink my design entirely.but I'd prefer 9 to 8.Īlternatively, quorum systems can support "zero-weight replicas" which effectively don't vote but still can be useful for eventually consistent reads. Likewise, if 5 aren't enough, I'd skip over 6 and go to 7. I'd guess that if you've got enough message queue traffic that 3 servers can't handle the load, those servers aren't a significant fraction of your total cost. Yes, 4 servers might handle more load than 3 servers, but so would 5 servers. ![]() ![]() (also note slow doesn't even mean the machine is having problems in geographically distributed setups it may just be due to physical distance from the leader.) Looking at it the other way, you go from having problems when 2/3 are slow/broken to having problems when 2/4 are slow/broken. Worse than useless from a quorum perspective, because you've increased the number of servers that have to participate in quorum (quickly) without increasing the number that don't.
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