[Pacemaker] dual drbd+active/active mysql is that possible?

[Gray Wen Wen]

hmmm... @Arnold...
you are correct.
Thanks your reply
"Yes, this can be made to work _if_ each
mysql-instance has its own disk-space for the tables."
this give me a hit...haha i think my mind is stuck at that time.

I already use active/Passive mode for my mysql cluster and it works fine
now.

thanks so much....




On Wed, Oct 9, 2013 at 3:56 AM, Arnold Krille <arnold at arnoldarts.de> wrote:

> On Sun, 6 Oct 2013 02:08:24 +0800 Gray Wen Wen
> <deutschland.gray at gmail.com> wrote:
> > Hi all,
> > now I am trying to configure a dual DRBD with mysql
> > i wanna use active/active mode without any loadbalance.
> > so my drbd is primary/primary on node1 and node2.
> > the mount point is /mysql
> > and i configure everything for mysql
> > then when I start the pacemaker service
> > the mysql can only be active on one node.
> > and another server show mysql startup error.
> >
> > I tried few times...so here is my question,
> > whether because of I set primay/primary drbd so actually the two
> > nodes hold the same shared storage (/mysql folder on two nodes)
> > so if one node start mysql that means it locks the folder /mysql
> > and another node can not continue use this shared storage.
> >
> > does mysql active/active mode must use loadblance or something else?
>
> How do you think mysql (or any other database) works?
> What happens when a row is added to a table? Now think about making
> mysql sync that process (adding a row to a table) across several
> instances, regardless whether these are all read-write masters or some
> just read-only slaves. Yes, this can be made to work _if_ each
> mysql-instance has its own disk-space for the tables. But these
> mysql-instances will get horribly confused when someone else modifies
> their disk-space without them knowing. Even if that "someone else" is
> another mysql-instance meaning to do the right thing. There is a reason
> why the second instance sees the tables as "locked".
>
> Long story short: Don't do what you are trying to do.
> Either use drbd in active-passive and run _one_ mysql-instance on the
> drbd-master. Or run one mysql instance with its own disk-space on each
> node and promote/demote the write-master/read-only-slave with the
> mysql-RA.
>
> Good luck,
>
> Arnold
>
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