Samsung has announced a 256 GB memory part based on the UFS 2.0 mobile standard [tomshardware.com], and it can reach faster sequential read speeds than commonplace SATA 3.0 (600 MB/s) [wikipedia.org] SSDs:
Samsung announced the industry's first 256GB embedded memory based on the Universal Flash Storage (UFS) 2.0 standard, which is meant to replace the eMMC standard. Samsung says that its new UFS 2.0 drive is faster even than some SATA-based SSDs for PCs.
[...] The new embedded storage module is based on Samsung's own V-NAND technology and comes with a "specially-designed high-performance controller." The latest UFS 2.0 memory supports up to 45,000 and 40,000 input/output operations per second (IOPS) for random reading and writing, respectively. That is twice as fast as the previous UFS generation that supported 19,000 and 14,000 IOPS for random read and write workloads.
Samsung's 256GB module achieves up to 850MB/s sequential read speed, which is twice as fast as many SATA SSDs. It also supports up to 256MB/s sequential write speed, which Samsung says is three times faster than what high-performance microSD cards can currently achieve.
UFS 2.0 parts could potentially reach even higher speeds [anandtech.com]:
While the new NAND definitely is part of the speed improvement, it couldn't have been achieved without an increase of the interface bandwidth. The new memory today is the first announced UFS 2.0 solution based on a 2-lane interface. The UFS 2.0 standard defines a lane running at up to HS Gear 3 at up to 600MB/s, so doubling up of the lanes gives a theoretical maximum of 1.2GB/s. It'll definitely be interesting to see what devices adopt this storage solution in the near future.