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

On 12/6/10 6:10 PM, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Mon, Dec 6, 2010 at 9:04 PM, Josh Berkus <josh@agliodbs.com> wrote:
>>> Actually, on OSX 10.5.8, o_dsync and fdatasync aren't even available.
>>> From my run, it looks like even so regular fsync might be better than
>>> open_sync.
> 
>> But I think you need to use fsync_writethrough if you actually want durability.
> 
> Yeah.  Unless your laptop contains an SSD, those numbers are garbage on
> their face.  So that's another problem with test_fsync: it omits
> fsync_writethrough.

Yeah, the issue with test_fsync appears to be that it's designed to work
without os-specific switches no matter what, not to accurately reflect
how we access wal.

I'll see if I can do better.

--                                  -- Josh Berkus                                    PostgreSQL Experts Inc.
                        http://www.pgexperts.com