The proceedings of HPDC'15 have been published within the ACM digital library. They can be found in there as follows:

HPDC'15: http://dl.acm.org/citation.cfm?id=2749246&CFID=678221897&CFTOKEN=49572642

Workshops:

BigSystem'15: http://dl.acm.org/citation.cfm?id=2756594&CFID=678221897&CFTOKEN=49572642
CLHS'15: http://dl.acm.org/citation.cfm?id=2752499&CFID=678221897&CFTOKEN=49572642
FTXS'15: http://dl.acm.org/citation.cfm?id=2751504&CFID=678221897&CFTOKEN=49572642
ROSS'15: http://dl.acm.org/citation.cfm?id=2768405&CFID=678221897&CFTOKEN=49572642
ScienceCloud'15: http://dl.acm.org/citation.cfm?id=2755644&CFID=678221897&CFTOKEN=49572642
SCREAM'15: http://dl.acm.org/citation.cfm?id=2753524&CFID=678221897&CFTOKEN=49572642
VTDC'15: http://dl.acm.org/citation.cfm?id=2755979&CFID=678221897&CFTOKEN=49572642