Adding memory to server in cluster

I was wondering if there is a way to add memory to a server in the cluster without losing the data we currently have. I tried removing the server and adding it back in with more memory allocated but looks like it will use the same memory quota that other servers in the cluster are using.
Say we already have 12GB worth of data on the Membase server and have allocated appropriate memory, then we have to add another 10GB worth of data and want to allocated additional memory to the servers, how would we do this without dropping the bucket altogether and reloading all the data?

Thanks
RV