A Closer Look
Every aspect of the Z400s is designed to reduce production costs. The drive itself is made to a level that would be unacceptable by an enthusiast's standards. The enclosure is almost entirely plastic, aside from thin metal inserts for mounting screws. And there isn't a single screw holding the chassis together.
Again, the Z400s ships in mSATA, M.2 and 2.5-inch form factors. Today we're testing the 2.5-inch 128GB model with a 7mm z-height.
Inside, there's a very small printed circuit board that takes up roughly one-third of the available space. Neither the controller nor the flash benefits from augmented cooling, though that shouldn't be an issue on an entry-level solution.
This is our lab's first outing with Silicon Motion's SM2246XT, from the same family as the SM2246EN (used in a large number of existing low-cost client SSDs). SanDisk pairs the processor with 15nm MLC NAND. The 128GB drive uses two flash packages with 64GB each. We suspect the 256GB model would simply double the number of packages to four.
Data Type Comparison And SLC Cache
Compressible and incomprehensible data are handled at the same rate on SanDisk's Z400s. Silicon Motion doesn't use a compression engine that penalizes write performance when working with incompressible data.
Don't let the terms DRAM-less, OEM and low-cost make you think this thing is a total dog. There are worse-performing drives with three-bit-per-cell flash shipping under the guise of low-cost solid-state drives. For instance, we recently reviewed Adata's 120GB SP550, which delivered sustained sequential writes of 66 MB/s with 64KB blocks.