A new voting scheme for replication management, called double voting, is proposed as a suitable solution to mobile groupware applications. In the traditional single voting scheme, long-duration failure is frequent in mobile and weakly-connected environments, and it causes deterioration of update commit rate because the vote weight of disconnected servers cannot be utilized. The double voting differs from traditional schemes in that we consider unexpected long-duration disconnection. To increase update availability, we improve single voting both by dividing servers into some groups and by taking second ballot with vote weight representing each group. We also develop a member exclusion protocol for a proxy server to detect disconnected servers and to encompass its vote weight, thus preventing loss of the total ballot. We present an analysis of the availability of the double voting and simulate the effect of group setting on commit rate and commit time. We also simulate the comparison of the double voting and the single voting.
