4 ms·

Because http://en.wikipedia.org/wiki/CAP_theorem http://en.wikipedia.org/wiki/CAP_theorem. It's a distributed system. You want it to keep working (be available

by harryh 13y ago

Because http://en.wikipedia.org/wiki/CAP_theorem http://en.wikipedia.org/wiki/CAP_theorem. It's a distributed system. You want it to keep working (be available) all the time right? Guess what, you're gonna have to lose some consistency.

AnthonyMouse 13y ago
For extremely high availability systems like this it is generally better to choose both consistency and availability at the expense of partition tolerance and then mitigate the possibility of partitions with meshed multiply redundant interconnects. Moreover, you don't strictly need a distributed system. You could instead elect one exchange at any given time as the primary and clear all inter-exchange trades through that exchange.
- harryh 13y ago
  It's really fun watching you turn into such a pretzel that you want to somehow get around the CAP theorem and/or go back to the days of monopoly exchanges all to get away from the horrible evil of a cost for liquidity of less than 0.1%. Don't miss the forest for the trees.
  - AnthonyMouse 13y ago
    Citing the CAP theorem as a reason not to have a distributed system is like citing Arrow's Impossibility Theorem as a reason not to have a representative democracy. Proving the impossibility of a platonic ideal doesn't tell you anything about whether one imperfect system is superior to another in practice. And you can't hand wave away the fact that the implications of the CAP theorem are minimal on a distributed system with a high level of interconnect redundancy. If you can ensure with high probability that there will not be a partition in the network then you don't need partition tolerance. If against all odds you have a partition anyway then you lose availability, but that isn't a characteristic unique to the CAP theorem or distributed systems -- any system will lose availability if enough redundant components fail simultaneously.
    - hft_throwaway 13y ago
      Exchange gateways fail, network lines fail. This happens all the time. In the current system I can still trade if NASDAQ goes down.

by harryh 13y ago

AnthonyMouse 13y ago

For extremely high availability systems like this it is generally better to choose both consistency and availability at the expense of partition tolerance and then mitigate the possibility of partitions with meshed multiply redundant interconnects. Moreover, you don't strictly need a distributed system. You could instead elect one exchange at any given time as the primary and clear all inter-exchange trades through that exchange.

harryh 13y ago
It's really fun watching you turn into such a pretzel that you want to somehow get around the CAP theorem and/or go back to the days of monopoly exchanges all to get away from the horrible evil of a cost for liquidity of less than 0.1%. Don't miss the forest for the trees.
- AnthonyMouse 13y ago
  Citing the CAP theorem as a reason not to have a distributed system is like citing Arrow's Impossibility Theorem as a reason not to have a representative democracy. Proving the impossibility of a platonic ideal doesn't tell you anything about whether one imperfect system is superior to another in practice. And you can't hand wave away the fact that the implications of the CAP theorem are minimal on a distributed system with a high level of interconnect redundancy. If you can ensure with high probability that there will not be a partition in the network then you don't need partition tolerance. If against all odds you have a partition anyway then you lose availability, but that isn't a characteristic unique to the CAP theorem or distributed systems -- any system will lose availability if enough redundant components fail simultaneously.
  - hft_throwaway 13y ago
    Exchange gateways fail, network lines fail. This happens all the time. In the current system I can still trade if NASDAQ goes down.