local host, source_stores, migrate_to, user = unpack(arg);

	for source_store in source_stores:gmatch("[^,]+") do

		local store_type = source_store:match("%-(%a+)$");

		if store_type then

			source_store = source_store:sub(1, -2-#store_type);

		end

		local storage = module:open_store(source_store, store_type);

		local target = assert(sm.load_driver(host, migrate_to));

		target = assert(target:open(source_store, store_type));

		local function migrate_user(username)

			module:log("info", "Migrating data for %s", username);

			local data, err = storage:get(username);

			assert(data or err==nil, err);

			assert(target:set(username, data));

		end

		if store_type == "archive" then

			function migrate_user(username)

				module:log("info", "Migrating archive items for %s", username);

				local count, errs = 0, 0;

				for id, item, when, with in storage:find(username) do

					local ok, err = target:append(username, id, item, when, with);

					if ok then

						count = count + 1;

					else

						module:log("warn", "Error: %s", err);

						errs = errs + 1;

					end

					if ( count + errs ) % 100 == 0 then

						module:log("info", "%d items migrated, %d errors", count, errs);

					end

				module:log("info", "%d items migrated, %d errors", count, errs);

		if arg[4] then

			for i = 4, #arg do

				migrate_user(arg[i]);

			end

		else

			for user in um.users(host) do

				migrate_user(user);

			end