Xyratex (XRTX +10%) rallies after activist firm Baker Street Capital discloses its stake is now at 23%, and issues an open letter in which it: 1) Nominates 3 board members. 2) Calls on Xyratex to halt its big investments in HPC and cloud hardware solutions, as well as curtail SG&A spending. 3) Estimates the company is trading at only 2.2x the EBITDA produced by its core storage system and hard drive equipment ops (exc. cash). Xyratex rose on Friday in spite of providing disappointing guidance to go with its FQ4 beat.