Re: Is full_page_writes=off safe in conjunction with

Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> On Sat, 2006-04-15 at 11:45 -0400, Tom Lane wrote:
>> No, we'll just change the test in xlog.c so that fullPageWrites is
>> ignored if XLogArchivingActive.

> I can see the danger of which you speak, but does it necessarily apply
> to all forms of backup?

No, but the problem is we're not sure which forms are safe; it appears
to depend on poorly-documented details of behavior of both the kernel
and the backup program --- details that might well vary from one version
to the next even of the "same" program. Given the variety of platforms
PG runs on, I can't see us expending the effort to try to monitor which
combinations it might be safe to not use full_page_writes with.

> It seems that we should write an API to allow a backup device to ask for
> blocks from the database.

I don't think we have the manpower or interest to develop and maintain
our own backup tool --- or tools, actually, as you'd at least want a tar
replacement and an rsync replacement. Oracle might be able to afford
to throw programmers at that sort of thing, but where are you going to
get volunteers for tasks as mind-numbing as maintaining a PG-specific
tar replacement?

regards, tom lane