To: "Scott Carey" <scott@richrelevance.com>
Cc: "Scott Marlowe" <scott.marlowe@gmail.com>,
	"Thomas Finneid" <tfinneid@student.matnat.uio.no>,
	"Craig Ringer" <craig@postnewspapers.com.au>,
	pgsql-performance@postgresql.org
Subject: Re: slow update of index during insert/copy
In-Reply-To: <a1ec7d000809011146x456b942eof33627c63f8a021a@mail.gmail.com>
	(Scott Carey's message of "Mon\, 1 Sep 2008 11\:46\:59 -0700")
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	<a1ec7d000809011146x456b942eof33627c63f8a021a@mail.gmail.com>
From: Gregory Stark <stark@enterprisedb.com>
Organization: EnterpriseDB
Date: Mon, 01 Sep 2008 20:41:48 +0100
Message-ID: <873akjodqb.fsf@oxford.xeocode.com>
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"Scott Carey" <scott@richrelevance.com> writes:

> On Raid Controllers and Dev machines:
>
> For a dev machine the battery backup is NOT needed.
>
> Battery back up makes a _production_ system faster:  In production, data
> integrity is everything, and write-back caching is dangerous without a
> battery back up.
>
> So:
> Without BBU:   Write-through cache = data safe in power failure; Write back
> cache = not safe in power failure.
> With BBU :   Both modes are safe on power loss.

This could be read the wrong way. With a BBU it's not that you can run the
drives in write-back mode safely. It's that you can cache in the BBU safely.
The drives still need to have their write caches off (ie, in write-through
mode).

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training!