On Saturday, June 15, 2013 8:29 PM Sawada Masahiko wrote: On Sat, Jun 15, 2013 at 10:34 PM, Amit kapila <amit.kap...@huawei.com> wrote: > > On Saturday, June 15, 2013 1:19 PM Sawada Masahiko wrote: > On Fri, Jun 14, 2013 at 10:15 PM, Amit Kapila <amit.kap...@huawei.com> wrote: >> On Friday, June 14, 2013 2:42 PM Samrat Revagade wrote: >>> Hello, >> >>>>> We have already started a discussion on pgsql-hackers for the problem of >>>>> taking fresh backup during the failback operation here is the link for >>>>> that: >>>>> >>>>> >>>>> http://www.postgresql.org/message-id/CAF8Q-Gxg3PQTf71NVECe-6OzRaew5pWhk7yQtb >>>>> jgwrfu513...@mail.gmail.com >>>>> >>>>> Let me again summarize the problem we are trying to address. >>>>> >>>>> >>>> How will you take care of extra WAL on old master during recovery. If it >>>> plays the WAL which has not reached new-master, it can be a problem. > >>> you means that there is possible that old master's data ahead of new >>> master's data. > >> I mean to say is that WAL of old master can be ahead of new master. I >> understood that >> data files of old master can't be ahead, but I think WAL can be ahead. > >>> so there is inconsistent data between those server when fail back. right? >>> if so , there is not possible inconsistent. because if you use GUC option >>> as his propose (i.g., failback_safe_standby_mode = remote_flush), >>> when old master is working fine, all file system level changes aren't >>> done before WAL replicated. > >> Would the propose patch will take care that old master's WAL is also not >> ahead in some way? >> If yes, I think i am missing some point.
> yes it will happen that old master's WAL ahead of new master's WAL as you > said. > but I think that we can solve them by delete all WAL file when old > master starts as new standby. I think ideally, it should reset WAL location at the point where new master has forrked off. In such a scenario it would be difficult for user who wants to get a dump of some data in old master which hasn't gone to new master. I am not sure if such a need is there for real users, but if it is there, then providing this solution will have some drawbacks. With Regards, Amit Kapila. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
