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 (www.ibm.com/support/knowledgecenter/STXKQY/gpfsclustersfaq.html).
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 and pool 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
|
X | The block size, subblock size, and number of subblocks per block of a file system are set when the file system is created and cannot be changed later. | 4 MiB |
| -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 Type of replication. |
X | X | whenpossible |
| -L LogFileSize to
specify the size of the internal log files. See GPFS recovery logs. |
X | X | See mmcrfs command. |
| -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 | The default value is relatime if minReleaseLevel is 5.0.0 or later when the file system is created. Otherwise the default value is 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 MiB |
| --log-replicas LogReplicas to specify the number of recovery log replicas. | X | X | none |
| --metadata-block-size MetadataBlockSize Specifies a metadata block size that is different from the data block size. This parameter requires a separate pool for metadata. See Block size and mmcrfs command. | X | NA | By default the metadata block size is the same as the block size. For more information about block size, see the entry for -B BlockSize earlier in this table. |
| --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. |
| --write-cache-threshold HAWCThreshold Specifies the maximum length in bytes of synchronous write requests that is initially buffered in the highly available write cache before being written back to primary storage. | X | NA | The default value is 0, which means that the option is disabled. |
| Notes:
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