On Sun, Jun 16, 2013 at 2:00 PM, Amit kapila <amit.kap...@huawei.com> wrote: > 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. I think that we can dumping data before all WAL files deleting. All WAL files deleting is done when old master starts as new standby.
Regards, ------- Sawada Masahiko -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
