Operating system calls
The most common interface to files residing in a GPFS file system is through normal file system calls to the operating system.
When a file is accessed, the operating system submits the request to the GPFS kernel extension, which attempts to satisfy the application request using data already in memory. If this can be accomplished, control is returned to the application through the operating system interface. If the data is not available in memory, the request is transferred for execution by a daemon thread. The daemon threads wait for work in a system call in the kernel, and are scheduled as necessary. Services available at the daemon level include the acquisition of tokens and disk I/O.
Operating
system calls operate on GPFS data
during:
- Opening of a file
- Reading of data
- Writing of data