[DRBD-user] drbd+mysql+innodb

Adam Goryachev mailinglists at websitemanagers.com.au
Thu Jun 13 07:52:50 CEST 2013

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 13/06/13 14:29, 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?

A fraction of common sense should tell you that this is baloney (well,

Consider, what does mysql need, in order to function properly?
A) The various binary/executable files and scripts
B) Probably some log files/directories (depending on config)
C) Maybe /run or /var/run etc to create some lock file or similar
D) The DB files

Do they claim that shutting down the machine, removing the drive,
installing into a new machine, and turning on the new machine will also
not work?

What is the difference to the above, compared to using DRBD to sync the
entire drive?

what is the difference is you only sync the DB directories but ensure
matching versions/locations of config files and executables?

MySQL doesn't read any magic number of figure and decide it's suddenly
on a different machine and not work (at least, open source, unlicensed
versions, maybe licensed/paid for versions are different). As long as
the files exist, in the expected locations, and are not corrupt, then it
will work.

Maybe you should be asking this question of the person who claims it
will not work, or at least provide the details of the claim (ie, why) or
a reference to the discussion where this was claimed etc...

Just my 2c... don't believe everything you read on the Internet, apply
your own common sense filter.


Adam Goryachev
Website Managers

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