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You skipped the second part of that. Unless your web application is running on the database server then you are no longer running single node, your web app and
by mason55 10y ago
You skipped the second part of that. Unless your web application is running on the database server then you are no longer running single node, your web app and db server can become partitioned.
- kerkeslager 10y agoAh, okay, I didn't understand that next part correctly the first time. So that does account for why the author says such systems are rare. But that doesn't really help me understand why CA can't exist. There are still systems that simply don't have network partitions. SQLite on the same phone as the app using it? As I said, it doesn't seem like we ignore the rare or uninteresting cases.
- jasonwatkinspdx 10y agoThe CAP theorem is fundamentally about distributed systems. The name is on the tin. It's not ignoring things, you're trying to pick an argument via examples outside the explicitly defined scope.
- wmf 10y agoClustered CA systems can exist and they corrupt data (maybe silently) when a partition happens. In most discussions it is taken for granted that people don't tolerate data corruption. Single-node "CA" systems are "available" under CAP's definition but not available under the common sense definition. A single hardware failure will take out the entire system (but in theory everything will be in perfect order after you restore from backups).
- tl 10y agoEven if your web app and database are on the same server, you may experience partitions between the client and server.
- Xorlev 10y agoYou can, but it's vastly less likely than networking partitions assuming your DB is operating as expected.