[fry_the_guy]

I think the better argument against the CAP theorem is that while it is true, is it not really that useful. If you have a database with nodes in three data centers, it is much more likely that one of the data centers becomes disconnected (partitioned) from the rest of the internet, rather than that the internet itself is partitioned. In this case, a CP system can still remain available to the internet, it just can't also remain available to the nodes within the disconnected data center.

https://foundationdb.com/white-papers/the-cap-theorem

[aphyr]

Meanwhile, http://blog.pagerduty.com/2013/04/outage-post-mortem-april-1...

[fry_the_guy]

Discussing the CAP theorem is a discussion on what is theoretically possible.

All I am claiming is that it is theoretically possible to make a CP system that, in practice, is highly available. That does not mean one actually exists.

[aphyr]

Absolutely agreed; I'm just saying that as the Pagerduty postmortem demonstrates, CP availability becomes trickier as you increase the number of sites--and there are unavoidable minimum latency bounds due to the speed of light. Those bounds may be unacceptably high; this is why Google Spanner chooses instead to enforce strong bounds on clock synchronization.