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Message-ID: <721b21dc0608091824j684dc35do887da4e1fa58069@mail.gmail.com>
Date: Wed, 9 Aug 2006 18:24:07 -0700
From: "Steve Poe" <steve.poe@gmail.com>
To: "Scott Marlowe" <smarlowe@g2switchworks.com>
Subject: Re: Postgresql Performance on an HP DL385 and
Cc: "Jim C. Nasby" <jnasby@pervasive.com>,
	"Luke Lonergan" <LLonergan@greenplum.com>,
	"Alex Turner" <armtuk@gmail.com>, pgsql-performance@postgresql.org
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Scott,

Do you know how to activate the writeback on the RAID controller from HP?

Steve

On 8/9/06, Scott Marlowe <smarlowe@g2switchworks.com> wrote:
>
> On Wed, 2006-08-09 at 16:11, Steve Poe wrote:
> > Jim,
> >
> > I'll give it a try. However, I did not see anywhere in the BIOS
> > configuration of the 642 RAID adapter to enable writeback. It may have
> > been mislabled cache accelerator where you can give a percentage to
> > read/write. That aspect did not change the performance like the LSI
> > MegaRAID adapter does.
>
> Nope, that's not the same thing.
>
> Does your raid controller have batter backed cache, or plain or regular
> cache?  write back is unsafe without battery backup.
>
> The default is write through (i.e. the card waits for the data to get
> written out before acking an fsync).  In write back, the card's driver
> writes the data to the bb cache, then returns on an fsync while the
> cache gets written out at leisure.  In the event of a loss of power, the
> cache is flushed on restart.
>

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Scott,<br><br>Do you know how to activate the writeback on the RAID controller from HP?<br><br>Steve<br><br><div><span class="gmail_quote">On 8/9/06, <b class="gmail_sendername">Scott Marlowe</b> &lt;<a href="mailto:smarlowe@g2switchworks.com">
smarlowe@g2switchworks.com</a>&gt; wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">On Wed, 2006-08-09 at 16:11, Steve Poe wrote:
<br>&gt; Jim,<br>&gt;<br>&gt; I'll give it a try. However, I did not see anywhere in the BIOS<br>&gt; configuration of the 642 RAID adapter to enable writeback. It may have<br>&gt; been mislabled cache accelerator where you can give a percentage to
<br>&gt; read/write. That aspect did not change the performance like the LSI<br>&gt; MegaRAID adapter does.<br><br>Nope, that's not the same thing.<br><br>Does your raid controller have batter backed cache, or plain or regular
<br>cache?&nbsp;&nbsp;write back is unsafe without battery backup.<br><br>The default is write through (i.e. the card waits for the data to get<br>written out before acking an fsync).&nbsp;&nbsp;In write back, the card's driver<br>writes the data to the bb cache, then returns on an fsync while the
<br>cache gets written out at leisure.&nbsp;&nbsp;In the event of a loss of power, the<br>cache is flushed on restart.<br></blockquote></div><br>

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