Message-ID: <48DA207D.6090000@netwolves.com>
Date: Wed, 24 Sep 2008 07:11:57 -0400
From: Steve Clark <sclark@netwolves.com>
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To: Scott Carey <scott@richrelevance.com>
CC: Bruce Momjian <bruce@momjian.us>, Greg Smith <gsmith@gregsmith.com>,
	Merlin Moncure <mmoncure@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: Intel's X25-M SSD
References: <Pine.GSO.4.64.0809192316340.19112@westnet.com>	
	<200809240324.m8O3Ovn06515@momjian.us>
	<a1ec7d000809232125w52b1122ema21a9958814224b2@mail.gmail.com>
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Scott Carey wrote:
> A fantastic review on this issue appeared in July:
> http://www.alternativerecursion.info/?p=106
> And then the same tests on a RiData SSD show that they are the same 
> drive with the same characteristics:
> http://www.alternativerecursion.info/?p=276
> 
> Most blamed it on MLC being "slow" to write compared to SLC.  
> Technically, it is slower, but not by a whole lot -- we're talking a low 
> level difference of tens of microseconds.  A 250ms latency indicates an 
> issue with the controller chip.  SLC and MLC share similar overall 
> performance characteristics at the millisecond level.  The truth is that 
> MLC designs were low cost designs without a lot of investment in the 
> controller chip.  The SLC designs were higher cost designs that focused 
> early on on making smarter and more expensive controllers.  SLC will 
> always have an advantage, but it isn't going to be by several orders of 
> magnitude like it was before Intel's drive appeared.  Its going to be by 
> factors of ~2 to 4 on random writes in the long run.  However, for all 
> flash based SSD devices, there are design tradeoffs to make.  Maximizing 
> writes sacrifices reads, maximizing random access performance reduces 
> streaming performance and capacity.  We'll have a variety of devices 
> with varying characteristics optimal for different tasks.
> 
> On Tue, Sep 23, 2008 at 8:24 PM, Bruce Momjian <bruce@momjian.us 
> <mailto:bruce@momjian.us>> wrote:
> 
>     Greg Smith wrote:
>      > On Mon, 8 Sep 2008, Merlin Moncure wrote:
>      >
>      > > What's interesting about the X25 is that they managed to pull the
>      > > numbers they got out of a MLC flash product.  They managed this
>     with a
>      > > DRAM buffer and the custom controller.
>      >
>      > I finally found a good analysis of what's wrong with most of the
>     cheap MLC
>      > drives:
>      >
>      >
>     http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3403&p=7
>     <http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3403&p=7>
>      >
>      > 240ms random write latency...wow, no wonder I keep hearing so
>     many reports
>      > of cheap SSD just performing miserably.  JMicron is one of those
>     companies
>      > I really avoid, never seen a design from them that wasn't cheap junk.
>      > Shame their awful part is in so many of the MLC flash products.
> 
>     I am surprised it too so long to identify the problem.
> 
>     --
>      Bruce Momjian  <bruce@momjian.us <mailto:bruce@momjian.us>>      
>      http://momjian.us
>      EnterpriseDB                             http://enterprisedb.com
> 
>      + If your life is a hard drive, Christ can be your backup. +
> 
>     --
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>     (pgsql-performance@postgresql.org
>     <mailto:pgsql-performance@postgresql.org>)
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> 
> 
Anybody know of any tests on systems that have specific filesystems for
flash devices?