I think the conclusion from the discussion is that O_DIRECT is in
addition to the sync method, rather than in place of it, because
O_DIRECT doesn't have the same media write guarantees as fsync(). Would
you update the patch to do O_DIRECT in addition to O_SYNC or fsync() and
see if there is a per
On Fri, Jun 03, 2005 at 09:43:13 -0700,
Mary Edie Meredith <[EMAIL PROTECTED]> wrote:
>
> Looking at this from another angle, is there really any way that you can
> say a write is truly guaranteed in the event of a failure? I think in
> the end to be safe, you cannot. That's why (and I'm not t
On Fri, 2005-06-03 at 10:37 +1000, Neil Conway wrote:
> On Thu, 2005-06-02 at 11:49 -0700, Mary Edie Meredith wrote:
> > My understanding is that O_DIRECT means "direct" as in "no buffering by
> > the OS" which implies that if you write from your buffer, the write is
> > not going to return unless
On Thu, 2005-06-02 at 11:49 -0700, Mary Edie Meredith wrote:
> My understanding is that O_DIRECT means "direct" as in "no buffering by
> the OS" which implies that if you write from your buffer, the write is
> not going to return unless the OS thinks the write is completed
Right, I think that's d
On Thu, 2005-06-02 at 11:39 +1000, Neil Conway wrote:
> On Wed, 2005-06-01 at 17:08 -0700, Mary Edie Meredith wrote:
> > I know I'm late to this discussion, and I haven't made it all the way
> > through this thread to see if your questions on Linux writes were
> > resolved. If you are still inter
On Wed, 2005-06-01 at 17:08 -0700, Mary Edie Meredith wrote:
> I know I'm late to this discussion, and I haven't made it all the way
> through this thread to see if your questions on Linux writes were
> resolved. If you are still interested, I recommend read a very good
> one page description of
On Mon, 2005-05-30 at 16:29 +1000, Neil Conway wrote:
> On Mon, 2005-05-30 at 10:59 +0900, ITAGAKI Takahiro wrote:
> > Yes, I've tested pgbench and dbt2 and their performances have improved.
> > The two results are as follows:
> >
> > 1. pgbench -s 100 on one Pentium4, 1GB mem, 2 ATA disks, Linux
On Mon, 2005-05-30 at 11:24 -0400, Tom Lane wrote:
> Wouldn't count on it :-(. One thing I'm particularly worried about is
> buffer cache consistency: does the kernel guarantee to flush any buffers
> it has that overlap the O_DIRECT write operation?
At least on Linux I believe the kernel guarante
Neil Conway <[EMAIL PROTECTED]> writes:
> On Mon, 2005-05-30 at 02:52 -0400, Tom Lane wrote:
> Well, that claims that "data is guaranteed to have been transferred",
> but transferred to *where* is the question :)
Oh, I see what you are worried about. I think you are right: what the
doc promises i
On Mon, 2005-05-30 at 10:59 +0900, ITAGAKI Takahiro wrote:
> Yes, I've tested pgbench and dbt2 and their performances have improved.
> The two results are as follows:
>
> 1. pgbench -s 100 on one Pentium4, 1GB mem, 2 ATA disks, Linux 2.6.8
>(attached image)
> tps | wal_sync_method
> ---
Tom Lane wrote:
Neil Conway <[EMAIL PROTECTED]> writes:
is opening a file with O_DIRECT sufficient to ensure that
a write(2) does not return until the data has hit disk?
Some googling suggests so, eg
http://www.die.net/doc/linux/man/man2/open.2.html
Really? On that page I read:
"O_DIRECT..
On Mon, 2005-05-30 at 02:52 -0400, Tom Lane wrote:
> Some googling suggests so, eg
> http://www.die.net/doc/linux/man/man2/open.2.html
Well, that claims that "data is guaranteed to have been transferred",
but transferred to *where* is the question :) Transferring data to the
disk's buffers and the
Neil Conway <[EMAIL PROTECTED]> writes:
> I wonder if we're benchmarking the right thing, though: is
> opening a file with O_DIRECT sufficient to ensure that a write(2) does
> not return until the data has hit disk?
Some googling suggests so, eg
http://www.die.net/doc/linux/man/man2/open.2.html
T
Neil Conway <[EMAIL PROTECTED]> wrote:
> > The patch adds a new choice "open_direct" to wal_sync_method.
> Have you looked at what the performance difference of this option is?
Yes, I've tested pgbench and dbt2 and their performances have improved.
The two results are as follows:
1. pgbench -s
ITAGAKI Takahiro wrote:
The patch adds a new choice "open_direct" to wal_sync_method.
It uses O_DIRECT flags for WAL writes, like O_SYNC.
Have you looked at what the performance difference of this option is?
For example, these benchmark results seem to indicate that an older
version of the pa
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