File system replication parameters

The metadata (inodes, directories, and indirect blocks) and data replication parameters are set at the file system level and apply to all files. They are initially set for the file system when issuing the mmcrfs command.

They can be changed for an existing file system using the mmchfs command. When the replication parameters are changed, files created after the change are affected. To apply the new replication values to existing files in a file system, issue the mmrestripefs command.

Metadata and data replication are specified independently. Each has a default replication factor of 1 (no replication) and a maximum replication factor with a default of 2. Although replication of metadata is less costly in terms of disk space than replication of file data, excessive replication of metadata also affects GPFS efficiency because all metadata replicas must be written. In general, more replication uses more space.