[DRBD-user] drbd+mysql+innodb

Dirk Bonenkamp - ProActive dirk at proactive.nl
Thu Jun 13 08:09:14 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.

Op 13-6-2013 7:52, Adam Goryachev schreef:
> 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,
> almost).
> 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.
You're right, but what they mean to tell that InnoDB stores it data in a
very different way and you can't copy stuff around as easy as with
MyISAM. With MyISAM, you just can take the files of a single database an
put them on any other MySQL machine and you're good. It is not that easy
with InnoDB. Having said that, InnoDB has some very nice live backup
tools, so no need to bother with a copy of the files. However I can
understand that this feels very safe... :-) Bottomline is, it will run
fine on top of DRBD, just keep the configs the same on both machines,
but you already wanted to do that. No problems with failovers and stuff.

@Eric: Did you have a look at Percona's version of MySQL? They have what
they call 'ExtraDB', which is just their tuned InnoDB version (backwards
compatible). Gives very good performance They also have a nice set of
tools to go with it, also for doing 'hot' backups. We hired one of their
consultants for our MyISAM to InnoDB migration and go some good tuning
and tips from it. Oh, I don't own any Percona stock, in case you wondered...

Kind regards,


ProActive Software <http://www.proactive.nl>
T 	023 - 5422299
www.proactive.nl <http://www.proactive.nl>
My status <skype:dirkbonenkamp?call>

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