From: Craig James <craig_james@emolecules.com>
To: Guy Rouillier <guyr-ml1@burntmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: Making the most of memory?
Date: Wed, 23 Jan 2008 13:06:22 -0800
Message-ID: <4797AC4E.6040007@emolecules.com> (raw)
In-Reply-To: <47979C15.3040406@burntmail.com>
References: <4796BE84.9030803@centriccrm.com>
<dcc563d10801222120q78e390dbj2b884eca729c2975@mail.gmail.com>
<B30794E6-CD2A-43C1-B431-E24B56FBFB1D@concursive.com>
<dcc563d10801231044p1dba892r9b8bf1269395f068@mail.gmail.com>
<47979C15.3040406@burntmail.com>
Guy Rouillier wrote:
> Scott Marlowe wrote:
>> I assume you're talking about solid state drives? They have their
>> uses, but for most use cases, having plenty of RAM in your server will
>> be a better way to spend your money. For certain high throughput,
>> relatively small databases (i.e. transactional work) the SSD can be
>> quite useful.
>
> Unless somebody has changes some physics recently, I'm not understanding
> the recent discussions of SSD in the general press. Flash has a limited
> number of writes before it becomes unreliable. On good quality consumer
> grade, that's about 300,000 writes, while on industrial grade it's about
> 10 times that. That's fine for mp3 players and cameras; even
> professional photographers probably won't rewrite the same spot on a
> flash card that many times in a lifetime. But for database
> applications, 300,000 writes is trivial. 3 million will go a lot longer,
> but in non-archival applications, I imagine even that mark won't take
> but a year or two to surpass.
One trick they use is to remap the physical Flash RAM to different logical addresses. Typical apps update a small percentage of the data frequently, and the rest of the data rarely or never. By shuffling the physical Flash RAM around, the media lasts a lot longer than a simple analysis might indicate.
Craig
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To: pgsql-performance@postgresql.org
Cc: craig_james@emolecules.com, guyr-ml1@burntmail.com
Subject: Re: Making the most of memory?
In-Reply-To: <4797AC4E.6040007@emolecules.com>
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