Message-ID: <49D39AFA.8000700@ummon.com>
Date: Wed, 01 Apr 2009 12:48:58 -0400
From: Stef Telford <stef@ummon.com>
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To: Scott Marlowe <scott.marlowe@gmail.com>
CC: Greg Smith <gsmith@gregsmith.com>, Mark Kirkwood <markir@paradise.net.nz>,
	Scott Carey <scott@richrelevance.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Raid 10 chunksize
References: <C5F14970.3CA1%scott@richrelevance.com>	
	<49D31E85.8050405@paradise.net.nz> <49D37CAA.6080100@ummon.com>	
	<alpine.GSO.2.01.0904011144270.23835@westnet.com>	
	<49D3932D.3080808@ummon.com>
	<dcc563d10904010941r283b7536g383c8daa8b933ce7@mail.gmail.com>
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Scott Marlowe wrote:
> On Wed, Apr 1, 2009 at 10:15 AM, Stef Telford <stef@ummon.com> wrote:
>   
>>     I do agree that the benefit is probably from write-caching, but I
>> think that this is a 'win' as long as you have a UPS or BBU adaptor,
>> and really, in a prod environment, not having a UPS is .. well. Crazy ?
>>     
>
> You do know that UPSes can fail, right?  En masse sometimes even.
>   
Hello Scott,
    Well, the only time the UPS has failed in my memory, was during the
great Eastern Seaboard power outage of 2003. Lots of fond memories
running around Toronto with a gas can looking for oil for generator
power. This said though, anything could happen, the co-lo could be taken
out by a meteor and then sync on or off makes no difference.
   
    Good UPS, a warm PITR standby, offsite backups and regular checks is
"good enough" for me, and really, that's what it all comes down to.
Mitigating risk and factors into an 'acceptable' amount for each person.
However, if you see over a 2x improvement from turning write-cache 'on'
and have everything else in place, well, that seems like a 'no-brainer'
to me, at least ;)

    Regards
    Stef