Cott Lang <cott@internetstaff.com> writes:
> However, unless I am mistaken, a baseline backup would need to be taken
> cold because you cannot take a consistent online backup of the data
> files without using file system snapshots or split mirrors, and even
> that's questionable.
No, it wouldn't. All you need is to archive WAL beginning from the last
checkpoint record before you begin to take the baseline backup. The
baseline backup would not be consistent in itself --- but replaying WAL
from the previous checkpoint to any time later than the end of the
backup would bring it to a consistent state. Missed updates in the
backup are essentially damage that would get repaired by replay.
There are a few trivial things that still have to be done before this
can be a reality (one I can think of is that WAL really needs to have
entries for file creation/deletion), but it's not that far off in terms
of the base mechanisms. Writing the management software is the main
task.
There is a lot more info available in the pghackers archives.
regards, tom lane