That results in something called split brain. There are methods to avoid this.
http://www.gluster.org/2012/06/healing-split-brain/
You can use a feature called quorum to make sure that you can write to all copies of the data before the write is committed.
http://community.gluster.org/q/how-do-i-use-the-quorum-feature-to-prevent-split-brain/
http://www.gluster.org/2012/06/healing-split-brain/
You can use a feature called quorum to make sure that you can write to all copies of the data before the write is committed.
http://community.gluster.org/q/how-do-i-use-the-quorum-feature-to-prevent-split-brain/