On Wed, Aug 18, 2010 at 9:48 AM, Derrick Rice <derrick.r...@gmail.com>wrote:
> I've been reading up on the documentation for WAL shipping and warm standby > configuration. One concern that I have (a common one, I'm sure) is that it > seems that after bringing a standby server up as primary, other standby > servers (including the original primary) need to be rebased before they can > read the new primary's WALs in continuous recovery mode. > > It seems that the cause of this is a change to the leading digit of the WAL > files: > > http://archives.postgresql.org/pgsql-general/2010-03/msg00985.php > http://archives.postgresql.org/pgsql-admin/2009-08/msg00179.php > > I was hoping that someone would shed some light on this situation with a > technical explanation. It's not clear to me why the WAL files are > incompatible or why the digit increases. What does that first digit mean to > postgresql? Is it possible to have the restore_command ignore the leading > digit? > > I expected the WAL files to be compatible. If I start two servers from the > same "disk image" and then they get the same exact changes recorded in WAL, > why should the next created WAL differ depending on which server creates > it? I imagine these two servers to have identical new versions of a "disk > image" after consuming the exact same WALs (one generated them, the other > read them). > > I'm surprised that this question doesn't come up more often or that there's > no explanation in the docs about why its necessary to rebase a primary that > went down gracefully (e.g. for planned maintenance) > > Thanks > > Derrick > Considering the high level of activity on this list, I'm surprised not to have any discussion on this yet. Please let me know if there is a better discussion area for this topic or if I can clarify / rephrase my question to make it more attractive. Barring that, I guess I'll dig into the ultimate documentation: source. Derrick
