Re: We really ought to do something about O_DIRECT and data=journalled on ext4

Josh Berkus <josh@agliodbs.com> writes:
> On 11/30/10 7:09 PM, Tom Lane wrote:
>> Josh Berkus <josh@agliodbs.com> writes:
>>> Apparently, testing for O_DIRECT at compile time isn't adequate.  Ideas?
>> 
>> We should wait for the outcome of the discussion about whether to change
>> the default wal_sync_method before worrying about this.

> Are we considering backporting that change?

> If so, this would be another argument in favor of changing the default.

Well, no, actually it's the same (only) argument.  We'd never consider
back-patching such a change if our hand weren't being forced by kernel
changes :-(

As things stand, though, I think the only thing that's really open for
discussion is how wide to make the scope of the default-change: should
we just do it across the board, or try to limit it to some subset of the
platforms where open_datasync is currently the default.  And that's a
decision that ought to be informed by some performance testing.
        regards, tom lane