GPFS: Administration and Programming Reference - IRA Home

-n NumNodes
The estimated number of nodes that will mount the file system. This is used as a best guess for
the initial size of some file system data structures. The default is 32. This value cannot be
changed after the file system has been created.
When you create a GPFS file system, you might want to overestimate the number of nodes that
will mount the file system. GPFS uses this information for creating data structures that are
essential for achieving maximum parallelism in file system operations (see Appendix A: GPFS
architecture in General Parallel File System: Concepts, Planning, and Installation Guide). Although
a large estimate consumes additional memory, underestimating the data structure allocation can
reduce the efficiency of a node when it processes some parallel requests such as the allotment of
disk space to a file. If you cannot predict the number of nodes that will mount the file system,
allow the default value to be applied. If you are planning to add nodes to your system, you should
specify a number larger than the default. However, do not make estimates that are not realistic.
Specifying an excessive number of nodes may have an adverse affect on buffer operations.
-N NumInodes
The maximum number of files in the file system. This value defaults to the size of the file system
at creation, divided by 1M, and can be specified with a suffix, for example 8K or 2M. This value is
also constrained by the formula:
maximum number of files = (total file system space/2) / (inode size + subblock size)
For file systems that will be doing parallel file creates, if the total number of free inodes is not
greater than 5% of the total number of inodes there is the potential for slowdown in file system
access. Take this into consideration when changing your file system.
-Q {yes | no}
Activates quotas automatically when the file system is mounted. The default is -Q no.
To activate GPFS quota management after the file system has been created:
1. Mount the file system.
2. To establish default quotas:
a. Issue the mmdefedquota command to establish default quota values.
b. Issue the mmdefquotaon command to activate default quotas.
3. To activate explicit quotas:
a. Issue the mmedquota command to activate quota values.
mmcrfs Command
b. Issue the mmquotaon command to activate quota enforcement.
-r DefaultDataReplicas
Default number of copies of each data block for a file. Valid values are 1 and 2, but cannot be
greater than MaxDataReplicas. The default is 1.
-R MaxDataReplicas
Default maximum number of copies of data blocks for a file. Valid values are 1 and 2 but cannot
be less than DefaultDataReplicas. The default is 1.
-S {yes | no}
Suppress the periodic updating of the value of atime as reported by the gpfs_stat(), gpfs_fstat(),
stat(), and fstat() calls. The default value is -S no. Specifying -S yes for a new file system results
in reporting the time the file system was created.
-v {yes | no}
Verify that specified disks do not belong to an existing file system. The default is -v yes. Specify -v
no only when you want to reuse disks that are no longer needed for an existing file system. If the
command is interrupted for any reason, you must use the -v no option on the next invocation of
the command.
Chapter 8. GPFS commands 123