Message-ID: <4D4AC37D.2070207@2ndquadrant.com>
Date: Thu, 03 Feb 2011 10:02:21 -0500
From: Greg Smith <greg@2ndquadrant.com>
User-Agent: Thunderbird 2.0.0.24 (X11/20100317)
MIME-Version: 1.0
To: Dan Birken <birken@gmail.com>
CC: Scott Marlowe <scott.marlowe@gmail.com>,
	pgsql-performance <pgsql-performance@postgresql.org>
Subject: Re: Which RAID Controllers to pick/avoid?
References: <AANLkTimyRh1ieWxpCo1ht2D1fkmL+Ca_8ABBEw6yN2WR@mail.gmail.com>
	<4D4A411A.3040102@2ndquadrant.com>
	<AANLkTinB98Wgk+pzA_A9Ro=LTtmJJXFrkLVVM6h_d+AP@mail.gmail.com>
	<4D4A4804.3040307@2ndquadrant.com>
	<AANLkTinFaFU=RUtfddYODoV9yHj-TfFc2XL7stg=NZaQ@mail.gmail.com>
In-Reply-To: <AANLkTinFaFU=RUtfddYODoV9yHj-TfFc2XL7stg=NZaQ@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Dan Birken wrote:
> - Is the supercap + flash memory considered superior to the BBU in 
> practice?  Is that type of system well tested?

The main risk is that it's a pretty new approach.  The standard BBU 
setup has been used for a long time now; this whole flash+supercap thing 
has only showed up in the last couple of years.  Theoretically it's 
better; the #1 weakness of the old battery setup was only surviving an 
outage of a few days, and storing to flash doesn't have that issue.  
It's just got the usual risks of something new.

> - Is the linux support of the LSI and Adaptec cards comparable?

Seems to be.  The latest versions of Adaptec's arcconf utility even 
provide about the same quality of command-line tools as LSI's megactl, 
after being behind in that area for a while.  Only quirk, and I can't 
say where this was the manufacturer of the box or not because they 
installed the base OS, is that the 5405 setup I saw didn't turn off the 
write caches on the individual drives of the system.  That's the 
standard safe practice and default for the LSI cards.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support  www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books