Subject: Re: hardare config question
From: Scott Marlowe <smarlowe@g2switchworks.com>
To: Tom Arthurs <tarthurs@jobflash.com>
Cc: erik.myllymaki@aviawest.com, Mark Lewis <mark.lewis@mir3.com>,
	Vivek Khera <vivek@khera.org>,
	Pgsql performance <pgsql-performance@postgresql.org>
In-Reply-To: <445651F1.9070307@jobflash.com>
References: <445236D5.5060509@aviawest.com>
	<3DFCE70E-E4BB-40AB-B27F-99E90E8159CA@khera.org>
	<1146246441.15712.41.camel@archimedes> <44564C3F.2040609@aviawest.com>
	<445651F1.9070307@jobflash.com>
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Date: Mon, 01 May 2006 13:51:55 -0500

On Mon, 2006-05-01 at 13:22, Tom Arthurs wrote:
> UPS does not protect against the tech behind the rack unplugging the 
> power cable, or an accidental power cycle from exercising the wrong 
> switch. :)  Both are probably more common causes of failure than a total 
> power outage.
> 
> Erik Myllymaki wrote:
> > I have been in discussion with 3ware support and after adjusting some 
> > settings, the 3ware card in RAID 1 gets better performance than the 
> > single drive. I guess this had everything to do with the write (and 
> > maybe read?) cache.
> >
> > Of course now i am in a dangerous situation - using volatile write 
> > cache without a BBU.
> >
> > If I were to use a UPS to ensure a soft shutdown in the event of power 
> > loss, am I somewhat as safe as if I were to purchase a BBU for this 
> > RAID card?

Nor does it prevent an electrician from dropping a tiny piece of wire
into a power conditioner, causing a feedback that blows the other two
power conditioners, all three industrial UPSes, and the switch that
allows the Diesal generator to take over.

When that happened to me, I had the only database server in the company
to come back up 100% in tact.  You can guess by now I also had the only
database server with battery backed cache...