GPFS: Administration and Programming Reference - IRA Home

1. Create a snapshot using the mmcrsnapshot command. For more information on snapshots, see
General Parallel File System: Advanced Administration Guide.
2. Open an inode scan on the snapshot using the gpfs_open_inodescan() subroutine.
3. Retrieve inodes using the gpfs_next_inode() subroutine.
4. Read the file data:
a. Open the file using the gpfs_iopen() subroutine.
b. Read the file using the gpfs_iread(), gpfs_ireadx(), or gpfs_ireaddir() subroutines.
c. Close the file using the gpfs_iclose() subroutine.
The gpfs_ireadx() subroutine is more efficient than read() or gpfs_iread() for sparse files and for
incremental backups. The gpfs_ireaddir() subroutine is more efficient than readdir(), because it returns
file type information. There are also subroutines for reading symbolic links, gpfs_ireadlink() and for
accessing file attributes, gpfs_igetattrs().
IBM has supplied a backup application program, tsbackup.C, to serve as an example. This example is
located in /usr/lpp/mmfs/samples/util and consists of these files:
v tsbackup.C - A utility for backing up a GPFS file system to a TSM server using TSM clients.
v tsbackup.h - A header file containing necessary declarations.
The tsbackup sample application is invoked by the mmbackup script in /usr/lpp/mmfs/bin, and it invokes
the mmexectsmcmd script in that same directory to drive TSM clients. These scripts may also be
examined as examples.
Chapter 3. Managing file systems 25