[Pacemaker] problems with cman + corosync + pacemaker in debian

[Florian Haas]

On Mon, Feb 20, 2012 at 10:16 PM, diego fanesi <diego.fanesi at gmail.com> wrote:
> Actually I'm studying this technology. This is only a test. I'm trying to
> understand all possible configuration and at the moment I have some problems
> to understand the differences among file systems. Now I'm trying to use
> ocfs2 and it seems to work well but what is the best alternative?

Both have their pros and cons, to the point that for most people the
question boils down to which FS is supported on their preferred
platform -- RHEL/CentOS normally only support GFS2, SLES only OCFS2.
But you're on Debian, where there's support for both, so it's up to
you to decide.

> My big question is when should I use one rather than another one? I know
> glusterfs and, If I'm right, it doesn't need drbd but it is slower than gfs2
> and ocfs2. If I understood you can have the best performance using ocfs2, so
> I'm trying to use it. In case split-brain happens what is the best?

Probably Gluster. :) Any single-instance storage filesystem (that's
what GFS2 and OCFS2 both are) will freeze, completely, on all nodes,
until the misbehaving nodes either return to the cluster, or can
successfully be fenced. That's a very well known aspect of these
filesystems and solving it is well understood, but still, if you're
looking for something simple in the face of split brain, you probably
can't beat Gluster.

> And with mysql. To realize two node active/active there are many ways. you
> can use mysql master/master ndb replication or put data folder in a drbd
> partition on ocfs2 with the option "external locking" activated.

Get that last idea out of your head immediately. And if you haven't
got a clue how NDB works, get _that_ idea out of your head, too.

> what is the
> fastest and the safest way? in the case of split-brain happen what is the
> best? in my opinion the best is drbd.

Yes, single-Primary DRBD with no cluster filesystem at all. No OCFS2,
no GFS2, no Gluster -- just straightforward ext3, ext4, or XFS. Look
at http://youtu.be/3GoT36cK6os for a tutorial.

Florian

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