[DRBD-user] yes you can mount the secondary read-only (bug reports)

Dave Dykstra dwdha at drdykstra.us
Tue Jan 4 18:03:22 CET 2005

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


On Tue, Jan 04, 2005 at 05:37:28PM +0100, Philipp Reisner wrote:
> Am Dienstag, 4. Januar 2005 15:55 schrieb Dave Dykstra:
> > The FAQ says that DRBD does not allow mounting the secondary, but I found
> > a way to do it.  If I start up DRBD on two nodes, make one primary but
> > not mount it there, then attempt to mount the secondary side it gets
> > mounted read-only.  Then I can mount the primary read-write.  This may
> > be considered a feature by some but I consider it a bug.  I accidentally
> > got into this situation by a misunderstanding of the parameter to the
> > heartbeat 'drbddisk' script when I configured heartbeat for the first
> > time and passed 'drbd0' to the script as an example showed rather than the
> > name I had chosen for my resource.  As a result, the primary & secondary
> > sides didn't get swapped, but heartbeat unmounted the primary side and
> > mounted the secondary.
> >
> 
> Unfortunately it is not possible to prohibit mounting it on the
> secondary under Linux-2.4.x
> 
> If you would retry on a Linux-2.6.x kernel, you will notice that 
> it fails on 2.6 .

It does prevent mounting when the primary side is mounted.  Why is there
a difference?  I suppose there must be something in the filesystem itself
that prevents allowing mounts from two places.  I forgot to mention it,
but I'm using an ext3 filesystem.  It might be worth failing all reads
if that's possible.

- Dave



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