Moving from 34nm to 25nm NAND flash Chips for SSDs

An industry switch is in progress from 34nm to 25nm flash chips for solid state drives. At least for Sandforce controller based products, the 25nm chips also requires new firmware to support the new chips.

The 25nm flash technology requires more “over provisioning” for capacities of 180GB and smaller, so a 120GB SSD becomes a 115GB, a 60GB becomes a 56GB; more of the flash must be set aside for wear and error correction. SSD capacities of 180GB and higher do not have a capacity hit.

These 25nm changes have brought on some questions about truth in advertising, which is discussed at StorageReview.com. In short, be aware of what you’re buying. You might want to peruse this forum post at OCZ. And apparently (post deleted), OCZ might yet have the pleasure of a consumer class action lawsuit courtesy Rosen Law Firm P.A. Why any business would want to put themselves at risk this way is beyond me. Maybe that law firm can take a look at Apple’s SSD capacity claims also.

Note that I do not recommend and have never recommended OCZ. And do not confuse OCZ with the OWC Mercury Pro RE SSDs that I use daily (600GB triple-SSD RAID-0 stripe of 200GB Mercury Extreme Pro RE).

My advice: know what you’re buying + don’t assume that all vendors are shipping product that is ready for prime time + too good a deal is not a deal.

A note on Tier 1 vs Tier 2 flash

Tier 1 parts have a manufacturer logo as well as a part number on them, generally laser etched onto them (of course shady resellers could fake that). Generally from Intel, Hynix, Toshiba, and Micron.

Tier 2 parts are blank and/or do not have a logo – generally lower grade parts.

Tier 1 flash chip