[DRBD-user] DRBD or not DRBD ?

Patrick Egloff pegloff at gmail.com
Sun Apr 24 06:59:07 CEST 2011

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


Hi and thanks for the answer !

I got several pm urging me NOT to use active/active and OCFS2.

A more simpler active/passive and no OCFS2 would be the best choice.... Too
many things could go wrong with OCFS2 and active/active + MySQL.

But you fully understood my configuration and thanks for your help.
My drbd.conf is almost like the one you sent me.

But in my case, i must have another problem.... it's not working.

One more question. I have 2 ethernet ports. eth1 is used to link both boxes
together.
Should i use for DRBD + Heartbeat a different IP address and class than on
eth0 which is on the LAN ?

Patrick

2011/4/22 Digimer <linux at alteeve.com>

> On 04/22/2011 01:36 PM, Patrick Egloff wrote:
> > Hi all,
> >
> > First of all, let me say that i'm a newbie with DRBD and not a high
> > level linux specialist...
>
> Few are. Fewer still who claim to be. :)
>
> > I want to have a HA setup for my Intranet which is using PHP + MySQL.
> > (Joomla 1.6)
> >
> > For that, i have 2 DELL servers with 5 HD RAID on which i installed a
> > CentOS 5.5 with
> >
> > I tried to install OCFS2, DRBD and Heartbeat as active/active. I'm at
> > the point where i can access to my drbd partition  /sda6, but i can't
> > make both boxes talk together.
> > I do have some errors will loading :
> > - mount.ocfs2 (device name specified was not found while opening device
> > /dev/drbd0)
> > - drbd is waiting for peer.... and i have to enter "yes" to stop the
> process
> >
> > After reading a lot, i'm not even sure anymore if my first project is
> > the right choice...
> >
> > Is the configuration i planned the best one for my usage or should i
> > change my plans for another setup with same result, that is high
> > availibility ?
> >
> > If it makes sense to continue with drbd , i will be back with some
> > questions about my problems...
> >
> >
> > Thanks,
>
> I can't speak to heartbeat or OCFS2, as I use RHCS and GFS2, but the
> concept should be similar. Aside from that, those are questions above
> DRBD anyway.
>
> First, your RAID 5 is done in hardware, so CentOS only sees /dev/sda,
> right? Second, Partition 6 is what you want to use as a backing device
> on either node for /dev/drbd0? If you want to run Active/Active, then
> you will also want Primary/Primary, right?
>
> Given those assumptions, you will need to have a drbd.conf similar to
> below. Note that the 'on foo {}' section must have the same hostname
> returned by `uname -n` from either node. Also, change the 'address' to
> match the IP address of the interface you want DRBD to communicate on.
> Lastly, make sure any firewall you have allows port 7789 on those
> interfaces.
>
> Finally, replace '/sbin/obliterate' with the path to a script that will
> kill (or mark Inconsistent) the other node in a split-brain situation.
> This is generally done using a fence device (aka: stonith).
>
> Line wrapping will likely make this ugly, sorry.
>
> ====
> #
> # please have a a look at the example configuration file in
> # /usr/share/doc/drbd83/drbd.conf
> #
>
> # The 'global' directive covers values that apply to RBD in general.
> global {
>        # This tells Linbit that it's okay to count us as a DRBD user. If
> you
>        # have privacy concerns, set this to 'no'.
>        usage-count     yes;
> }
>
> # The 'common' directive sets defaults values for all resources.
> common {
>        # Protocol 'C' tells DRBD to not report a disk write as complete
> until
>        # it has been confirmed written to both nodes. This is required for
>        # Primary/Primary use.
>        protocol        C;
>
>        # This sets the default sync rate to 15 MiB/sec. Be careful about
>        # setting this too high! High speed sync'ing can flog your drives
> and
>        # push disk I/O times very high.
>        syncer {
>                rate    15M;
>        }
>
>        # This tells DRBD what policy to use when a fence is required.
>        disk {
>                # This tells DRBD to block I/O (resource) and then try to
> fence
>                # the other node (stonith). The 'stonith' option requires
> that
>                # we set a fence handler below. The name 'stonith' comes
> from
>                # "Shoot The Other Nide In The Head" and is a term used in
>                # other clustering environments. It is synonomous with with
>                # 'fence'.
>                fencing         resource-and-stonith;
>        }
>
>        # We set 'stonith' above, so here we tell DRBD how to actually fence
>        # the other node.
>        handlers {
>                # The term 'outdate-peer' comes from other scripts that flag
>                # the other node's resource backing device as
> 'Inconsistent'.
>                # In our case though, we're flat-out fencing the other node,
>                # which has the same effective result.
>                outdate-peer    "/sbin/obliterate";
>        }
>
>        # Here we tell DRBD that we want to use Primary/Primary mode. It is
>        # also where we define split-brain (sb) recovery policies. As we'll
> be
>        # running all of our resources in Primary/Primary, only the
>        # 'after-sb-2pri' really means anything to us.
>        net {
>                # Tell DRBD to allow dual-primary.
>                allow-two-primaries;
>
>                # Set the recover policy for split-brain recover when no
> device
>                # in the resource was primary.
>                after-sb-0pri   discard-zero-changes;
>
>                # Now if one device was primary.
>                after-sb-1pri   discard-secondary;
>
>                # Finally, set the policy when both nodes were Primary. The
>                # only viable option is 'disconnect', which tells DRBD to
>                # simply tear-down the DRBD resource right away and wait for
>                # the administrator to manually invalidate one side of the
>                # resource.
>                after-sb-2pri   disconnect;
>        }
>
>        # This tells DRBD what to do when the resource starts.
>        startup {
>                # In our case, we're telling DRBD to promote both devices in
>                # our resource to Primary on start.
>                become-primary-on       both;
>        }
> }
>
> # The 'resource' directive defines a given resource and must be followed
> by the
> # resource's name.
> # This will be used as the GFS2 partition for shared files.
> resource r0 {
>        # This is the /dev/ device to create to make available this DRBD
>        # resource.
>        device          /dev/drbd0;
>
>        # This tells DRBD where to store it's internal state information. We
>        # will use 'internal', which tells DRBD to store the information at
> the
>        # end of the resource's space.
>        meta-disk       internal;
>
>        # The next two 'on' directives setup each individual node's
> settings.
>        # The value after the 'on' directive *MUST* match the output of
>        # `uname -n` on each node.
>        on an-node01.alteeve.com {
>                # This is the network IP address on the network interface
> and
>                # the TCP port to use for communication between the nodes.
> Note
>                # that the IP address below in on our Storage Network. The
> TCP
>                # port must be unique per resource, but the interface itself
>                # can be shared.
>                # IPv6 is usable with 'address ipv6 [address]:port'.
>                address         192.168.2.71:7789;
>
>                # This is the node's storage device that will back this
>                # resource.
>                disk            /dev/sda6;
>        }
>
>        # Same as above, but altered to reflect the second node.
>        on an-node02.alteeve.com {
>                address         192.168.2.72:7789;
>                disk            /dev/sda6;
>        }
> }
> ====
>
> --
> Digimer
> E-Mail: digimer at alteeve.com
> AN!Whitepapers: http://alteeve.com
> Node Assassin:  http://nodeassassin.org
>



-- 
Patrick Egloff - TK5EP
email : pegloff at gmail.com
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