[DRBD-user] DRBD Recovery actions without Pacemaker

Klint Gore kgore4 at une.edu.au
Fri Jul 8 05:14:42 CEST 2016

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


From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of James Ault
Sent: Friday, 8 July 2016 2:02 AM
To: James Ault; drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] DRBD Recovery actions without Pacemaker

I see the Manual Failover section of the DRBD 8.4.x manual, and I see that it requires that the file system be umounted before attempting to promote and mount the file system on the secondary.

What I meant by "those status flags" in my first message is that when a node mounts a file system, that file system is marked as mounted somewhere on that device.   The "mounted" status flag is what I'm trying to describe, and I'm not sure if I have the correct name for it.
Does pacemaker or manual failover handle the case where a file server experiences a hard failure where the umount operation is impossible?    How can the secondary copy of the file system be mounted if the umount operation never occurred and cannot occur on server1?

The basic manual failover described in the manual is when you choose manually switch over to the other machine.  You would use that if you wanted to do maintenance on the primary.
If the primary dies by itself, you don’t need to unmount it - that’s where fencing comes into play.  You need to make sure that the “dead” node is well and truly dead and going to stay that way.
What you’re trying to achieve is the same as what my setup is.  On both servers, nothing starts at boot and only the root file system mounts from fstab.  A script is run to make one of them primary, mount the file systems of the drbd devices, add the external ip,  start the network services.  The other node just becomes drbd secondary and that’s it.  At failover, the dead machine is pulled from the rack and taken away, then the secondary becomes primary, mounts the file systems of the drbd devices, adds the external ip, starts the network services.  If I’m doing manual failover for maintenance, then on the primary, the network services are stopped, the external ip address is removed, the file systems are unmounted, drbd is demoted to secondary.  The other machine is promoted just like hardware failover.
Klint.
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