So would using Neon negate the need for something like Citus for scaling out a postgres database?
Why use Paxos instead of Raft?
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Re: Why use Paxos instead of Raft?
#12So would using Neon negate the need for something like Citus for scaling out a postgres database?
It's a different approach, planetscale and Citus are sharding that is intended to be mostly transparent. It's not 100% transparent, but both get pretty close.
Neon is more of an aurora approach detaching storage from the compute, you could scale up to more replicas and it could enable other functionality, though Postgres already can handle a pretty high replica count so you can scale out reads that way.
Re: Why use Paxos instead of Raft?
#13The author is here, happy to answer questions if any.
if storage and compute are separated - how is storage mounted on to the compute? Generally you can attach a volume only to one server at a time
Re: Why use Paxos instead of Raft?
#14I'm curious how many nodes end up in the consensus group, presumably you don't want more than 3 because throughput scales 1/N, unless their implementation can alleviate that significantly.
Re: Why use Paxos instead of Raft?
#15I used to work in the orbit of a distinguished eng at AWS who was famous for saying something to the effect of, "At the bottom of any scaled distributed system is either Paxos, or a bug."
It's a fun quote, it reminds me of the "every sufficiently advanced program contains a bug-ridden implementation of half of common lisp", or something along those lines. But there really is a wide world of distributed consensus systems out there (although Paxos is easily the most elegant).
Re: Why use Paxos instead of Raft?
#16This is a great writeup, thanks. It will be very useful if y'all could add a post comparing neon with citusdb in terms of functionality, performance and operations.
Re: Why use Paxos instead of Raft?
#17This is a great writeup, thanks. It will be very useful if y'all could add a post comparing neon with citusdb in terms of functionality, performance and operations.
Let us work on it! Short answer is Neon is most similar to AWS Aurora - 100% compatibility with Postgres and all the innovation is on storage and serverless. The use case is core database for apps.
And Citus is shared nothing architecture plus columnstores. This means the use case is analytics or mixed workloads. Citus people should comment on this of course.
Re: Why use Paxos instead of Raft?
#18The author is here, happy to answer questions if any.
if storage and compute are separated - how is storage mounted on to the compute? Generally you can attach a volume only to one server at a time
We changed Postgres to send WAL to safekeepers and read from page servers: https://neon.tech/blog/architecture-decisions-in-neon/
Re: Why use Paxos instead of Raft?
#19I used to work in the orbit of a distinguished eng at AWS who was famous for saying something to the effect of, "At the bottom of any scaled distributed system is either Paxos, or a bug."
It's a fun quote, it reminds me of the "every sufficiently advanced program contains a bug-ridden implementation of half of common lisp", or something along those lines. But there really is a wide world of distributed consensus systems out there (although Paxos is easily the most elegant).
There's a variation of this on the subject of distributed systems re: Erlang/BEAM VM
Re: Why use Paxos instead of Raft?
#20I used to work in the orbit of a distinguished eng at AWS who was famous for saying something to the effect of, "At the bottom of any scaled distributed system is either Paxos, or a bug."
When I was at AWS I heard the same phrase from a DE, probably the same guy, and once heard him also say "Raft is just a special case of Paxos to try to simplify it, but regular Paxos isn't actually that hard, just use Paxos".
I was fairly junior at the time, and Raft seemed much more approachable, but after really forcing myself to read and understand the Paxos paper, I see what he meant. I am pretty sure most of the love for Raft was that the original whitepaper was just a better presentation. The actual Paxos algorithm is quite simple.
If you go into Raft already having mastered Paxos (as this DE was doing), it's clear that Raft is basically isomorphic to a special case of Paxos.