DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma;
	h=mime-version:in-reply-to:references:date:message-id:subject:from:to
	:cc:content-type:content-transfer-encoding;
	b=h8aJlVqY/2W5qxxRsK7K4rDC4wNkyCuNZkDgX7JxknfrWPhaVs4xiKIhO9B0c3kSQ3
	H1Czr4QFJF+iOHrXHVzm16pwe50d7YPeq2ypSgEsGjBRAS8a669Mv8RXXsTk54e+0PYI
	X1o5zF1lvf+oNDfzJ0VgBh1cLDpwplWQKhFrA=
MIME-Version: 1.0
In-Reply-To: <4B8331D5.7000802@2ndquadrant.com>
References: <201002211410.o1LEAht05941@momjian.us>
	<4B814920.1040204@cheapcomplexdevices.com>
	<4B82187A.7060604@2ndquadrant.com> <4B822DFF.50501@tweakers.net>
	<4B8329A3.4040003@2ndquadrant.com> <4B832B3E.9080207@mark.mielke.cc>
	<4B8331D5.7000802@2ndquadrant.com>
Date: Mon, 22 Feb 2010 19:21:40 -0700
Message-ID: <dcc563d11002221821p773906a5hf3d3ffaf39bbddc6@mail.gmail.com>
Subject: Re: SSD + RAID
From: Scott Marlowe <scott.marlowe@gmail.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: Mark Mielke <mark@mark.mielke.cc>,
	Arjen van der Meijden <acmmailing@tweakers.net>,
	pgsql-performance@postgresql.org
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

On Mon, Feb 22, 2010 at 6:39 PM, Greg Smith <greg@2ndquadrant.com> wrote:
> Mark Mielke wrote:
>>
>> I had read the above when posted, and then looked up SRAM. SRAM seems to
>> suggest it will hold the data even after power loss, but only for a peri=
od
>> of time. As long as power can restore within a few minutes, it seemed li=
ke
>> this would be ok?
>
> The normal type of RAM everyone uses is DRAM, which requires constrant
> "refresh" cycles to keep it working and is pretty power hungry as a resul=
t.
> =A0Power gone, data gone an instant later.

Actually, oddly enough, per bit stored dram is much lower power usage
than sram, because it only has something like 2 transistors per bit,
while sram needs something like 4 or 5 (it's been a couple decades
since I took the classes on each).  Even with the constant refresh,
dram has a lower power draw than sram.