[DRBD-user] 3 simple questions for a nifty setup

David david at davidbranford.net
Wed Aug 24 17:16:30 CEST 2005

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

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com
> [mailto:drbd-user-bounces at lists.linbit.com]On Behalf Of paddy
> Sent: Wednesday, 24 August 2005 8:52 PM
> To: DRBD List
> Subject: Re: [DRBD-user] 3 simple questions for a nifty setup
> On Wed, Aug 24, 2005 at 12:01:35AM +0930, David wrote:
> > Hi all,
> >
> > Just thought I'd dig this one up out of the archives as it
> interests me to
> > know more on some progress, if it has been made:
> >
> > > -----Original Message-----
> > > From: drbd-user-bounces at lists.linbit.com
> > > [mailto:drbd-user-bounces at lists.linbit.com]On Behalf Of paddy
> > > Sent: Friday, 1 July 2005 5:05 AM
> > > To: drbd-user at lists.linbit.com
> > > Subject: Re: [DRBD-user] 3 simple questions for a nifty setup
> > >
> <snip>
> >
> > Paddy,
> >
> > Have you made any more progress on your mysql install on top of
> DRBD yet?
> I have a running system which is sufficient for my needs, which
> are only little.
> I need to post here to seek help with tuning drbd timeouts, so please see
> that for details.
> Sadly, my application does not stretch the setup, and my
> experience of mysql
> is largely confined to it just working, so I couldn't recommend anyone to
> follow in my footsteps, unless perhaps they were doing the same
> silly thing I am!

Thanks paddy for your reply. I think I am better understanding the
differences - I am not after the full-scale mysql clustering solution; I
don't need it/have the resources.

What do you mean when you say you have mysql running on top of drbd? Have
you got both PC's mysql data directories separate, or do they share the same
data files? (ie. /mnt/drbd0/var/lib/mysql)

I was wondering if such a setup as the latter is possible, since it seems
logical to me and pretty straight-forward; if a server running mysql
crashes, it must reboot and recover. If the primary server of a two-server
heartbeat "cluster" crashes, same thing - it's just a different machine
which must recover from the cluster, it is not privy to any extra/different
information... or is it?

Does anybody see any danger with this proposed setup? Anybody actually doing

> > I
> > am interested in doing the same, but if I go the 'proper' mysql
> cluster way,
> > I need 3 machines, and I only have 2.
> My limited understanding was that mysql supports two different
> architectures:
> replication and clustering.  The replication is asynchronous master->slave
> (and thus requires a minimum of only two boxes), while the clustering is
> truly multi-master and synchronous, but requires the whole database to be
> loaded in RAM (which is out of the question for my app).  When I
> looked at
> postgres I thought it was a similar story there, but I thought I saw
> something the other day suggesting otherwise.  Sorry I don't recall the
> details.
> If you're even considering the 'proper mysql cluster' side by
> side against the
> kind of thing I'm doing, then I suggest you look very carefully at your
> requirements as they are really _not_ the same thing.
> Where mysql on drbd has been a win for me is in admin time.

What do you mean by mysql on drbd - could you say (briefly) how you have
mysql running on drbd (ie. which files are available to which servers?)

Thanks again,


> It
> has enabled
> me to use generic technologies like drbd and ipsec to solve multiple
> problems, rather than getting tangled up in stuff like the mysql/openssl
> licensing problem and configuring several different distribution systems.
> Many thanks to all who work on it.
> Regards,
> Paddy
> --
> Perl 6 will give you the big knob. -- Larry Wall
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