On 4/5/2013 10:32 AM, Gregory Farnum wrote:
On Fri, Apr 5, 2013 at 10:28 AM, Dimitri Maziuk <dmaziuk@xxxxxxxxxxxxx> wrote:
On 04/05/2013 10:12 AM, Wido den Hollander wrote:
Think about it this way. You have two racks and the network connection
between them fails. If both racks keep operating because they can still
reach that single monitor in their rack you will end up with data
inconsistency.
Yes. In DRBD land it's called 'split brain' and they have (IIRC) entire
chapter in the user manual about picking up the pieces. It's not a new
problem.
You should place mon.c outside rack A or B to keep you up and running in
this situation.
It's not about racks, it's about rooms, but let's say rack == room ==
colocation facility. And I have two of those.
Are you saying I need a 3rd colo with all associated overhead to have a
usable replica of my data in colo #2?
Or just a VM running somewhere that's got a VPN connection to your
room-based monitors, yes. Ceph is a strongly consistent system and
you're not going to get split brains, period. This is the price you
pay for that.
-Greg
Software Engineer #42 @ http://inktank.com | http://ceph.com
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The point is I believe that you don't need a 3rd replica of everything,
just a 3rd MON running somewhere else.
Jeff
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