求助，升级了一下两年没升级的 archlinux， postgresql 挂了。。

以前没咋用过 linux 。最近用一个两年没 syu 的 archlinux 服务器，装啥都出奇怪的问题，但也不敢升级，上面跑着好多东西呢，怕出问题。刚才实在忍不了了，战战兢兢的 pacman -syu 了，结果，当真， owncloud 挂了，分析是由于 postgresql 挂了引起的。求助，哪位能指点一下么。。

还有，如果删除再重装 pgsql 的话，原来的数据库咋保留？网上查的都是在服务运行的状态下 dump ，再升到高版本的 reload ，可我已经升级了，并且服务也不启动了。

# systemctl start postgresql

Job for postgresql.service failed because the control process exited with error code.
See "systemctl status postgresql.service" and "journalctl -xe" for details.

# systemctl status postgresql.service

postgresql.service - PostgreSQL database server
Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Fri 2017-04-14 02:09:00 ; 7min ago
Process: 26394 ExecStop=/usr/bin/pg_ctl -s -D ${PGROOT}/data stop -m fast (code=exited, status=0/SUCCESS)
Process: 5814 ExecStartPre=/usr/bin/postgresql-check-db-dir ${PGROOT}/data (code=exited, status=1/FAILURE)
Main PID: 17344 (code=exited, status=0/SUCCESS)

Apr 14 02:09:00 xxx.xxx systemd[1]: Starting PostgreSQL database server...
Apr 14 02:09:00 xxx.xxx postgres[5814]: An old version of the database format was found.
Apr 14 02:09:00 xxx.xxx postgres[5814]: You need to dump and reload before using PostgreSQL 9.6.
Apr 14 02:09:00 xxx.xxx postgres[5814]: See http://www.postgresql.org/docs/9.6/static/upgrading.html
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Control process exited, code=exited status=1
Apr 14 02:09:00 xxx.xxx systemd[1]: Failed to start PostgreSQL database server.
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Unit entered failed state.
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Failed with result 'exit-code'.

# journalctl -xe

Unit postgresql.service has begun starting up.
Apr 14 02:09:00 xxx.xxx postgres[5814]: An old version of the database format was found.
Apr 14 02:09:00 xxx.xxx postgres[5814]: You need to dump and reload before using PostgreSQL 9.6.
Apr 14 02:09:00 xxx.xxx postgres[5814]: See http://www.postgresql.org/docs/9.6/static/upgrading.html
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Control process exited, code=exited status=1
Apr 14 02:09:00 xxx.xxx systemd[1]: Failed to start PostgreSQL database server.
-- Subject: Unit postgresql.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit postgresql.service has failed.
--
-- The result is failed.
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Unit entered failed state.
Apr 14 02:09:00 xxx.xxx systemd[1]: postgresql.service: Failed with result 'exit-code'.