What is this nand thing?

[Ian Lepore]

On Sun, 2012-12-30 at 18:03 -0500, Brett Wynkoop wrote:
> Greeting-
> 
> What is this nand that I am reading about on the list?  I have a
> feeling it is not a NAND GATE we are speaking of.
> 
> -Brett
> 

Nand flash storage.  It's the same stuff that's in an sdcard or a usb
thumb drive.  Some embedded systems have the bare storage chip on the
board, without the microcontrollers found in sdcards et. al.  The nand
subsystem in freebsd is an in-kernel implementation of what those
microcontrollers do (ecc calculations, managing bad blocks, in general
the sort of thing that makes a bare chip into a mass storage device).  

The nandfs is a filesystem specially tailored for the needs of nand
storage (and that's really about all I know about it; I'm unclear on how
it stores its metadata and how the garbage collection stuff works).

-- Ian