The second JLESC summer school was held at BSC from July 2 to 3, 2015, following the 3rd JLESC Workshop at Barcelo Sants Hotel in Barceonla. The summer school was supported by the PUF in the context of the NEXTGN project. Its theme was on I/O, storage and data analytic techniques. The school was offered to students (mainly PhD students and post-docs) of the collaboration and open to students and faculties outside of the collaboration, if room. Up to a maximum of 24 students were considered.