Re: Intel's X25-M SSD - Mailing list pgsql-performance

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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>
Anybody know of any tests on systems that have specific filesystems for
flash devices?