File system creation considerations
File system creation involves anticipating usage within the file system and considering your hardware configurations. Before creating a file system, consider how much data will be stored and how great the demand for the files in the system will be.
Each of these factors can help you to determine how much disk resource to devote to the file system, which block size to choose, where to store data and metadata, and how many replicas to maintain. For the latest supported file system size, see the IBM Spectrum Scale™ FAQ in IBM® Knowledge Center.
Your GPFS™ file system is created by issuing the mmcrfs command. Table 1 details the file system creation options specified on the mmcrfs command, which options can be changed later with the mmchfs command, and what the default values are.
To move an existing file system into a new GPFS cluster, see Exporting file system definitions between clusters.
| Options | mmcrfs | mmchfs | Default value |
|---|---|---|---|
| Device name of the file system. | X | X | none |
| DiskDesc for each
disk in your file system. Note: The use of disk descriptors is discouraged.
|
X | Issue the mmadddisk or mmdeldisk command to add or delete disks from the file system. | none |
| -F StanzaFile specifies
a file that contains a list of NSD stanzas. For more information, see Stanza files. |
X | Issue the mmadddisk or mmdeldisk command to add or delete disks as indicated in the stanza file. | none |
| -A {yes | no | automount} to determine when to mount the file system. | X | X | yes |
| -B BlockSize to
set the data block size: 64K, 128K, 256K, 512K, 1M, 2M,
4M, 8M or 16M. See Block size. |
X | This value cannot be changed without re-creating the file system. | 256K |
| -D {posix | nfs4} semantics for a deny-write open lock | X | X | nfs4 |
| -E {yes | no} to
report exact mtime values. See mtime values. |
X | X | yes |
| -i InodeSize to set the size of inodes: 512, 1024, or 4096 bytes. | X | This value cannot be changed. | 4096 |
| -j {cluster | scatter} to
determine the block allocation map type. See Block allocation map. |
X | NA | See Block allocation map. |
| -k {posix | nfs4 | all} to determine the authorization types supported by the file system. | X | X | all |
| -K {no | whenpossible | always} to
enforce strict replication. See Strict replication. |
X | X | whenpossible |
| -L LogFileSize to
specify the size of the internal log files. See GPFS recovery logs. |
X | X | The default is 4 MB or the metadata block size, whichever is larger. |
| -m DefaultMetadataReplicas | X | X | 1 |
| -M MaxMetadataReplicas | X | This value cannot be changed. | 2 |
| -n NumNodes that will mount the file system. | X | X | 32 |
| -o MountOptions to be passed to the mount command. | NA | X | none |
| -Q {yes | no} to
activate quota. See Enabling quotas. |
X | X | no |
| -r DefaultDataReplicas | X | X | 1 |
| -R MaxDataReplicas | X | This value cannot be changed. | 2 |
| -S {yes | no | relatime} to
control how the atime value is updated. See atime values. |
X | X | no |
| -t DriveLetter See Windows drive letter. |
X | X | none |
| -T Mountpoint See Mountpoint directory. |
X | X | /gpfs/DeviceName |
| -V {full | compat} to change the file system format to the latest level. | NA | X | none |
| -v {yes | no} to
verify disk usage. See Verifying disk usage. |
X | NA | yes |
| -W NewDeviceName to assign a new device name to the file system. | NA | X | none |
| -z {yes | no} to
enable DMAPI See Enabling DMAPI. |
X | X | no |
| --filesetdf to specify (when quotas are enforced for a fileset) whether the df command will report numbers based on the quotas for the fileset and not for the total file system. | X | X | --nofilesetdf |
| --inode-limit MaxNumInodes [:NumInodesToPreallocate] to
determine the maximum number of files in the file system. See Specifying the maximum number of files that can be created. |
X | X | file system size/1 MB |
| --log-replicas LogReplicas to specify the number of recovery log replicas. | X | X | none |
| --metadata-block-size MetadataBlockSize to
specify the block size for the system storage pool. See Block size. |
X | NA | The default is the same as the value set for -B BlockSize. |
| --mount-priority Priority to control the order in which the individual file systems are mounted at daemon startup or when one of the all keywords is specified on the mmmount command. | X | X | 0 |
| --perfileset-quota to set the scope of user and group quota limit checks to the individual fileset level. | X | X | --noperfileset-quota |
| --rapid-repair to keep track of incomplete replication on an individual file block basis (as opposed to the entire file). | NA | X | none |
| --version VersionString to enable only the file system features that are compatible with the specified release. | X | NA | The default value is defined by the current committed function level for the cluster minReleaseLevel, for example 4.2.2.0 or other values, depending on the cluster. |
| Notes:
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