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I have to find a database that will ensure the UDP replication intercontinental.

  1. Do you know if there is any SQL database that will support UDP replication?

  2. If not, can I use MySQL replication (TCP/IP protocol) intercontinental (from China to Switzerland)? Will this work fine? Won't be any meltdowns? How can I prevent them?

  3. The master will be in China and the slave in Switzerland. If the slave will be down for a long period of time, and the logs used to update the replications will be too big or not enough, how can I handle the replication? What is the solution?

Thank you and kind regards,

Andreea

T. Andreea
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2 Answers2

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Years ago, I was DBA for a system that was replicating from USA to China (many years ago). An earthquake happened in the Pacific, disrupting most traffic to/from east Asia. Connections were flaky for most of a day, by which time traffic had been rerouted (I guess) through the Suez Canal instead of the Pacific Ocean. Slave connections came and went, but MySQL replication survived.

"UDP is faster" -- I suggest that this is an 'uninformed' reason. MySQL uses TCP/IP because it needs to know that the packets arrive at the other end. With UDP, replication can break due to network issues, and MySQL would not know it. That leads to a much worse mess than being "slower".

CH:CN might be about 250ms -- that is network travel time. One packet will take that long, whether you are using TCP/IP or UDP. TCP/IP will seem slower because it will send only a certain number of packets before waiting for ACK/NAK. That can (and should) probably be tuned due to the long distance.

Once you have done that low level tuning (at the OS, not MySQL), TCP/IP will be about as fast as UDP. But reliability is the real reason to tell your client to jump in a lake. (Sorry, I don't know the OS tunables.)

As for Replication being "down for a long time"... (I assume you mean hours or days.) Yes, you should plan for such. Set expire_logs_days to a high enough number. I like 14; that's days.) Plus have monitoring to see if things have gone bad. UDP can't help with the network being down.

Rick James
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It's been a while since I used it, but I think SAP SQL Anywhere (formerly Sybase SQL Anywhere, and Watcom SQL before that) allowed replication by a variety of protocols, including UDP.

I have not used any recent versions, but I did use it several years ago when I worked for a software vendor that authored an accounting package, and we used it as an inexpensive database server. It was really a nice product.

mannaggia
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