Re: [DRBD-user] drbd+mysql+innodb

[Paul Walsh]

Title: ProActive Software

On 13/06/13 05:29, Robinson, Eric wrote: I really appreciate everyone's input but everyone misunderstood the question I was really asking. It's my fault for mentioning rsync. I fully understand the difference between how rsync works and how drbd works. We use them both all the time. But the real question is more high level. We have been told that even if you stop the mysql service, you still cannot backup an innodb database by simply copying the files from one server to another. We have been told that the mysql service will not start properly on the new server even if you make a 100% exact copy of all the files from the old server. If that is true, I don't understand how using drbd can work with innodb tables, since it basically just makes a copy of the files to another server. Am I asking the question right?   -- Eric Robinson   For what it's worth, we run MySQL+InnoDB on DRBD and use Heartbeat+Pacemaker for failover between nodes at different sites.  This supports our Moodle VLE which is an important part of our course provision.  As yet we have had no problems. We also use mysqldump to back up databases. To quote from Wikipedia: " InnoDB recovers from a crash or other unexpected shutdown by replaying its logs" These logs, by nature of the fact they're on a DRBD device, will be identical on both nodes, so if, say, node-A fails, node-B can assume Primary role for the DRBD device and mysql can start up, replaying its logs to may sure the data is up-to-date. I think whoever told you mysql would not start properly was possibly referring to what would happen if you simply copied all the files (with, for instance, rsync) whilst the database was active. -- Paul Walsh Head of Unix/Linux Systems Services, Corporate ICT, Birmingham City University, City North Campus, Perry Barr, BIRMINGHAM B42 2SU, UK Tel: +44 (0)121 331 5708 Fax: +44 (0)121 356 2875 Mobile: +44 (0)7974 150 421

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