Parallel Input/Output System, PIOUS

The concept of a parallel file system for workstation clusters was presented in 1993 by Moyer and Sunderam (see [MS93]). PIOUS supports process groups on a heterogeneous workstation cluster in accessing common data on disk drives. The first version of PIOUS tries to cover the following issues:

• Independence of the underlying file system and the transport mechanisms to allow portability to other systems. PIOUS only requires reliable data transfer mechanisms between cooperating workstations.

• Execution of operations is asynchronous to use full parallelism of a system.

• Files are stored in a distributed manner to guarantee scalability.

• Integrated control of parallelism and mechanisms for fault tolerance. Fault tolerance is achieved by replicating data on several disks.

• Currently there exists no knowledge about an optimal structure of such a file system. Therefore, PIOUS has a flexible design that allows to change the user interface and the internal data structures.

PIOUS consists of a set of PIOUS data servers (PDS) which coordinate the offered services and a set of library calls where the library has to be linked to the application program. PDS access data on disk drives and run on every workstation which has at least one part of a distributed file. They run independently and are controlled by the PIOUS service coordinator (PSC). Library functions transfer I/O calls to a set of PDS/PSC requests.

PIOUS defines so called ``parafiles''. These are 2 dimensional file structures where the segments are scattered block-wise over the disks. For a more detailed description of this data structure and a performance analysis of PIOUS see [MS93].