The Good News:
Parallel file systems are available. For example:
GPFS: General Parallel File System for AIX (IBM)
Lustre: for Linux clusters (Intel)
PVFS/PVFS2: Parallel Virtual File System for Linux clusters (Clemson/Argonne/Ohio State/others)
PanFS: Panasas ActiveScale File System for Linux clusters (Panasas, Inc.)
HP SFS: HP StorageWorks Scalable File Share. Lustre based parallel file system (Global File System for Linux) product from HP
The parallel I/O programming interface specification for MPI has been available since 1996 as part of MPI-2. Vendor and "free" implementations are now commonly available.