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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: We really ought to do something about O_DIRECT and data=journalled on ext4
Date: 2010-12-07 02:10:13
Message-ID: 6815.1291687813@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Dec 6, 2010 at 9:04 PM, Josh Berkus <josh(at)agliodbs(dot)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.

regards, tom lane

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