GPFS: Administration and Programming Reference - IRA Home

The system displays information similar to:
replication factors
metadata(max) data(max) file [flags]
------------- --------- ---------------
1 ( 2) 1 ( 2) /fs1/project4.sched
1 ( 2) 1 ( 2) /fs1/project4.resource
See the “mmlsattr Command” on page 196 for complete usage information. See the General Parallel File
System: Concepts, Planning, and Installation Guide and search on GPFS architecture and file system
creation considerations for a detailed discussion of file system attributes.
Changing file replication attributes
Use the mmchattr command to change the replication attributes for one or more files.
You can only increase data and metadata replication as high as the maximum data and maximum
metadata replication factors for that file system. You cannot change the maximum data and maximum
metadata replication factors once the file system has been created.
Specify the file name, attribute, and new value with the mmchattr command. For example, to change the
metadata replication factor to 2 and the data replication factor to 2 for the file named project7.resource in
the file system fs1, enter:
mmchattr -m 2 -r 2 /fs1/project7.resource
To confirm the change, enter:
mmlsattr /fs1/project7.resource
The system displays information similar to:
replication factors
metadata(max) data(max) file [flags]
------------- --------- ---------------
2 ( 2) 2 ( 2) /fs1/project7.resource
See the “mmchattr Command” on page 81 and the “mmlsattr Command” on page 196 for complete usage
information. See the General Parallel File System: Concepts, Planning, and Installation Guide and search
on GPFS architecture and file system creation considerations for a detailed discussion of file system
attributes.
When considering data replication for files accessible to SANergy, see SANergy export considerations in
General Parallel File System: Advanced Administration Guide.
Using Direct I/O on a file in a GPFS file system
The Direct I/O caching policy can be set for files in a GPFS file system by specifying the -D option on the
mmchattr command.
This caching policy bypasses file cache and transfers data directly from disk into the user space buffer, as
opposed to using the normal cache policy of placing pages in kernel memory. Applications with poor cache
hit rates or very large I/Os may benefit from the use of Direct I/O.
Direct I/O may also be specified by supplying the O_DIRECT file access mode on the open() of the file.
Restriping a GPFS file system
Writing data into a GPFS file system correctly stripes the file. However, if you have added disks to a GPFS
file system that is seldom updated, use the mmrestripefs command to restripe the file system to achieve
maximum performance.
Chapter 3. Managing file systems 19