[Discuss] SSD: enterprise vs. consumer Flash

[srehrlich at gmail.com (Scott Ehrlich)]

On Sun, Jun 3, 2012 at 10:55 PM, Tom Metro <tmetro+blu at gmail.com> wrote:
> Richard Pieri wrote:
>> There ain't no such thing as "high end" flash chips in the way that
>> you're thinking. ?High end in the NAND flash arena is a matter of
>> sustained write performance. ?That's it. ?Not quality. ?Not reliability.
>> Speed.
>
> Hmmm...that's *exactly* the way that I was thinking. Earlier in this
> thread I wrote, "...it seems likely that the mid-range SSDs are going to
> be using higher density chips, with faster write speeds, both of which
> will lead to lower production yields and thus higher prices."
>
>
>> The thing is, flash read and write speeds have a technical
>> plateau so you won't see much difference in the raw performance of
>> different manufacturers' chips of a given generation.
>
> I'll buy that, but I'm still skeptical that a $20 USB drive has the same
> chips in it as a $200 SSD, let alone a $1000 SSD.
>
>
>> The difference is how different vendors optimize their controllers.
>
> Makes sense.
>
>
>> So how do the likes of EMC and Violin go so much faster for so much
>> longer (5-10 years vs. 6-24 months for commodity SSD)? ?Several things.
>> They use battery-backed DRAM cache on their controllers.
>
> So more silicon...
>
>
>> The typical consumer-grade SSD has a single big flash chip in it. ?An
>> enterprise class SSD has banks of chips arranged in something similar to
>> a RAID 0 configuration to reap the benefits of more "spindles".
>
> So more chips...
>
>
>> Enterprise-class SSDs can have 100-200% over-provisioning or more.
>
> So more silicon...
>
>
>> All of this comes at a premium.
>
> Yes, these are all plausible reasons for why an enterprise SSD costs
> more than a consumer SSD. But the situation you described is a far cry
> from the scenario Ed suggested where the exact same type and quantity of
> Flash chips simply have a different controller chip added and it doubles
> or triples the price. That was the bit I was skeptical of.
>
> Thanks for the additional detail.
>
> ?-Tom

When you have a chance, if you haven't seen it already, check out the
videos on youtube by Scott Moulton, aka SuperFlyflippingA.   He is a
Digital Forensics and hard drive expert, and his videos will provide
great details on the inner-workings of both mechanical and SSD drives,
along with how chip selection is managed by the vendors.

Scott

>
> --
> Tom Metro
> Venture Logic, Newton, MA, USA
> "Enterprise solutions through open source."
> Professional Profile: http://tmetro.venturelogic.com/
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