[Discuss] SSD: enterprise vs. consumer Flash

[richard.pieri at gmail.com (Richard Pieri)]

On Jun 2, 2012, at 6:09 PM, 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.  The primary difference is the controllers used for their respective interfaces.  Different manufacturers may have different degrees of quality, but if you compare Sandisk with Sandisk you'll find the same flash chips inside.

> Elsewhere in this thread the different types of Flash - multi- (cheaper)
> and single- (high-end) level Flash were mentioned.

Multi-level cell (MLC) flash is still NAND flash.  MLC offers higher bit densities but that doesn't change the fundamental nature of it being NAND flash.  It isn't somehow "better" or "worse" than any other kind of NAND flash unless a particular manufacturer has incorporated more or better quality control than the competitors.

> 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?  It's not that it implements a better SATA protocol or superior form of RAID-5.  It's the features ranging from hot-plug to automatic verification and correction that it offers.  The fact that the backing store is NAND flash rather than high-speed aluminum alloy changes nothing.


>> 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.

--Rich P.