[Discuss] SSD: enterprise vs. consumer Flash

[tmetro+blu at gmail.com (Tom Metro)]

Richard Pieri wrote:
> Tom Metro wrote:
>> Edward Ned Harvey wrote:
>>> The flash they use in USB sticks and SD cards is the same flash
>>> they use in enterrpise hard drives.
>> Are you sure about that?
> 
> He's right. USB flash and SSD flash both use NAND flash as opposed to
> NOR flash.

Just because both use parts from the same technology family doesn't mean
they are the same part.


> ...if you compare Sandisk with Sandisk you'll find the same flash
> chips inside.

So you're saying if I crack open a Sandisk USB drive and a Sandisk
enterprise SSD I'll find chips with identical part numbers inside? Call
me skeptical...


>> What makes an enterprise SSD controller more reliable? Or are you
>> saying the controller itself isn't more reliable, but it implements
>> hardware wear-leveling algorithms that makes the overall SSD more
>> reliable?
> 
> What makes a 3ware RAID card more reliable than a Marvel RAID card?

I'm not so sure it is. Is the MTBF of the *card* (significantly) any
different? I doubt it.

I suspect he is talking about the reliability of the storage system
improving as a result of a more sophisticated controller, but this
wasn't clear, and thus I asked. I wouldn't have phrased it as the
*controller* being more reliable.


>>> Flash itself is dirt cheap.  What you're really buying is the
>>> on-device flash controller, that maps the flash blocks to virtual
>>> HDD blocks, and implements the USB/SATA operations.
>> Are you sure about that?
> 
> He's correct on this as well.  NAND flash is cheap.  Controller
> circuits aren't so cheap, particularly when a small number of
> manufacturers are investing heavily in performance wars.

The Flash chips have commodity volume production in their favor (which
can be significant). If the SSD's with high-end controllers are also
using high-end Flash chips that are produced in smaller volumes, then
this advantage is nullified.

Beyond that, the economics of semiconductor fabrication would suggest
this is incorrect, but I'll happily read reference material saying the
contrary, if you have it.

 -Tom

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