A SEF Unit is a set of dies and the associated control logic and (optional) DRAM. User-defined lists of dies form a many-to-one mapping of dies to a virtual device. A virtual device represents physical isolation with the number of virtual devices limited by the number of dies in the SEF Unit. Figure 3 shows an example of three virtual devices overlaid on an 8 x 4 SEF Unit with eight dies left unallocated.
Figure 3: SEF Unit Geometry
As shown in Figure 4, a die is a set of blocks. The blocks are the erase unit for a SEF Unit and consist of a set of pages. A page spans the die planes and is the programing unit. A plane is made up of atomic data units (ADUs). An ADU is the read/write unit holding both user data and metadata. Metadata consists of a user-defined tag data (UA) and a configured number of user supplied metadata (MD).