mmcrfs command
Creates a GPFS™ file system.
Synopsis
mmcrfs Device {"DiskDesc[;DiskDesc...]" | -F StanzaFile}
[-A {yes | no | automount}] [-B BlockSize] [-D {posix | nfs4}]
[-E {yes | no}] [-i InodeSize] [-j {cluster | scatter}]
[-k {posix | nfs4 | all}] [-K {no | whenpossible | always}]
[-L LogFileSize] [-m DefaultMetadataReplicas]
[-M MaxMetadataReplicas] [-n NumNodes] [-Q {yes | no}]
[-r DefaultDataReplicas] [-R MaxDataReplicas]
[-S {yes |
no
| relatime}] [-T Mountpoint] [-t DriveLetter]
[-v {yes | no}] [-z {yes | no}] [--filesetdf | --nofilesetdf]
[--inode-limit MaxNumInodes[:NumInodesToPreallocate]]
[--log-replicas LogReplicas] [--metadata-block-size MetadataBlockSize]
[--perfileset-quota | --noperfileset-quota]
[--mount-priority Priority] [--version VersionString]
[--write-cache-threshold HAWCThreshold]
Availability
Available on all IBM Spectrum Scale™ editions.
Description
Use the mmcrfs command to create a GPFS file system. The first parameter must be Device and it must be followed by either DiskDescList or -F StanzaFile. You can mount a maximum of 256 file systems in an IBM Spectrum Scale cluster at any one time, including remote file systems.
- For more information about the effects of block size, see the following paragraphs and the description of the -B parameter in this topic.
- For more information about replication factors, see the descriptions of the -m, -M, -r, and -R parameters in this topic.
- For more information about the maximum number of files (number of inodes), see the description
of the --inode-limit parameter in this topic.Note: In a file system that does parallel file creates, the number of free inodes must be greater than 5% of the total number of inodes. If not, the performance of the file system can be degraded. To increase the number of inodes, issue the mmchfs command.
A block is the largest contiguous amount of disk space that can be
allocated to a file and is therefore the largest amount of data that can be accessed in a single I/O
operation. The block size determines the maximum size of a read or write request that the file
system can send to the device driver. See the description of the -B
parameter in this topic.
A subblock is the smallest unit of contiguous disk space that can be
allocated to a file. The size of a subblock and the number of subblocks in a block depend on the
block size. A fragment is a contiguous group of one or more subblocks.
Files smaller than one block size are stored in one or more subblocks.
Large files are stored in a number of full blocks plus zero or more subblocks to hold the data at
the end of the file.
- For better performance, it is a good idea to set the block size to the same value as either the
application buffer size, the RAID stripe size, or a multiple of the RAID stripe size. If the block
size does not match the RAID stripe size, file system performance can be severely degraded,
especially for write requests.Note: For IBM Spectrum Scale RAID, the block size must equal the vdisk track size. For more information, see the online documentation for IBM Spectrum Scale RAID in IBM® Knowledge Center.
- In file systems with a high degree of variance in the size of files within the file system,
using a small block size has a large impact on performance when accessing large files. In this kind
of system it is suggested that you use a block size of 256 KiB (8 KiB sub-block). Even if only 1% of
the files are large, the effects on the file system are as follows:
- The amount of space that is taken by the large files usually dominates the amount of space that is used on disk.
- The waste in the subblocks that are used for small files is usually insignificant.
- The effect of block size on file system performance greatly depends on the application I/O pattern:
- A larger block size is often beneficial for large sequential read and write workloads.
A smaller block size can offer better performance for applications that perform small random writes to sparse files or small random writes to large files that are subject to frequent snapshots.
For block sizes larger than the default size of 4 MiB, it is a good idea to increase the page pool size in proportion to the block size. The reason is that the efficiency of many algorithms that rely on caching file data in a GPFS page pool depends more on the number of blocks cached than on the absolute amount of data. For a page pool of a given size, a larger block size results in fewer blocks cached.
- The block size for a file system cannot exceed the maximum block size that is set in the maxblocksize attribute. If you need a larger block size, first increase the value of maxblocksize. For more information, see mmchconfig command.
- For more information about choosing a block size, see Block size.
Results
- The mount point directory is created.
- The file system is formatted.
DiskName:::DiskUsage:FailureGroup::StoragePool:
For backward compatibility, the mmcrfs command still accepts the
traditional disk descriptors, but their use is deprecated.Parameters
- Device
- The device name of the file system to be created.
File system names need not be fully-qualified. fs0 is as acceptable as /dev/fs0. However, file system names must be unique within a GPFS cluster. Do not specify an existing entry in /dev.
This must be the first parameter.
- "DiskDesc[;DiskDesc...]"
- A descriptor for each disk to be included. Each descriptor is separated by a semicolon (;). The entire list must be enclosed in quotation marks (' or "). The use of disk descriptors is discouraged.
- -F StanzaFile
- Specifies a file containing the NSD stanzas and pool stanzas
for the disks to be added to the file system. NSD stanzas have this format:
%nsd: nsd=NsdName usage={dataOnly | metadataOnly | dataAndMetadata | descOnly} failureGroup=FailureGroup pool=StoragePool servers=ServerList device=DiskName
where:
- nsd=NsdName
- The name of an NSD previously created by the mmcrnsd command. For a list of available disks, issue the mmlsnsd -F command. This clause is mandatory for the mmcrfs command.
- usage={dataOnly | metadataOnly | dataAndMetadata | descOnly}
- Specifies the type of data to be stored on the disk:
- dataAndMetadata
- Indicates that the disk contains both data and metadata. This is the default for disks in the system pool.
- dataOnly
- Indicates that the disk contains data and does not contain metadata. This is the default for disks in storage pools other than the system pool.
- metadataOnly
- Indicates that the disk contains metadata and does not contain data.
- descOnly
- Indicates that the disk contains no data and no file metadata. Such a disk is used solely to keep a copy of the file system descriptor, and can be used as a third failure group in certain disaster-recovery configurations. For more information, see the IBM Spectrum Scale: Administration Guide and search for "Synchronous mirroring utilizing GPFS replication"
- failureGroup=FailureGroup
- Identifies the failure group to which the disk belongs. A failure group
identifier can be a simple integer or a topology vector that consists of up to three comma-separated
integers. The default is -1, which indicates that the disk has no point of failure in common with
any other disk.
GPFS uses this information during data and metadata placement to ensure that no two replicas of the same block can become unavailable due to a single failure. All disks that are attached to the same NSD server or adapter must be placed in the same failure group.
If the file system is configured with data replication, all storage pools must have two failure groups to maintain proper protection of the data. Similarly, if metadata replication is in effect, the system storage pool must have two failure groups.
Disks that belong to storage pools in which write affinity is enabled can use topology vectors to identify failure domains in a shared-nothing cluster. Disks that belong to traditional storage pools must use simple integers to specify the failure group.
- pool=StoragePool
- Specifies the storage pool to which the disk is to be assigned.
If this name is not provided, the default is system.
Only the system storage pool can contain metadataOnly, dataAndMetadata, or descOnly disks. Disks in other storage pools must be dataOnly.
- servers=ServerList
- A comma-separated list of NSD server nodes. This clause is ignored by the mmcrfs command.
- device=DiskName
- The block device name of the underlying disk device. This clause is ignored by the mmcrfs command.
Pool stanzas have this format:%pool: pool=StoragePoolName blockSize=BlockSize usage={dataOnly | metadataOnly | dataAndMetadata} layoutMap={scatter | cluster} allowWriteAffinity={yes | no} writeAffinityDepth={0 | 1 | 2} blockGroupFactor=BlockGroupFactor
where:
- pool=StoragePoolName
- Is the name of a storage pool.
- blockSize=BlockSize
- Specifies the block size of the disks in the storage pool.
- usage={dataOnly | metadataOnly | dataAndMetadata}
- Specifies the type of data to be stored in the storage pool:
- dataAndMetadata
- Indicates that the disks in the storage pool contain both data and metadata. This is the default for disks in the system pool.
- dataOnly
- Indicates that the disks contain data and do not contain metadata. This is the default for disks in storage pools other than the system pool.
- metadataOnly
- Indicates that the disks contain metadata and do not contain data.
- layoutMap={scatter | cluster}
- Specifies the block allocation map type. When allocating blocks for a given file, GPFS first uses a round-robin algorithm to spread the data across
all disks in the storage pool. After a disk is selected, the location of the data block on the disk
is determined by the block allocation map type. If cluster is specified,
GPFS attempts to allocate blocks in clusters. Blocks that
belong to a particular file are kept adjacent to each other within each cluster. If
scatter is specified, the location of the block is chosen randomly.
The cluster allocation method may provide better disk performance for some disk subsystems in relatively small installations. The benefits of clustered block allocation diminish when the number of nodes in the cluster or the number of disks in a file system increases, or when the file system's free space becomes fragmented. The cluster allocation method is the default for GPFS clusters with eight or fewer nodes and for file systems with eight or fewer disks.
The scatter allocation method provides more consistent file system performance by averaging out performance variations due to block location (for many disk subsystems, the location of the data relative to the disk edge has a substantial effect on performance). This allocation method is appropriate in most cases and is the default for GPFS clusters with more than eight nodes or file systems with more than eight disks.
The block allocation map type cannot be changed after the storage pool has been created.
- allowWriteAffinity={yes | no}
- Indicates whether the File Placement Optimizer (FPO) feature is to be enabled for the storage pool. For more information on FPO, see File Placement Optimizer
- writeAffinityDepth={0 | 1 | 2}
- Specifies the allocation policy to be used by the node writing the data.
A write affinity depth of 0 indicates that each replica is to be striped across the disks in a cyclical fashion with the restriction that no two disks are in the same failure group. By default, the unit of striping is a block; however, if the block group factor is specified in order to exploit chunks, the unit of striping is a chunk.
A write affinity depth of 1 indicates that the first copy is written to the writer node. The second copy is written to a different rack. The third copy is written to the same rack as the second copy, but on a different half (which can be composed of several nodes).
A write affinity depth of 2 indicates that the first copy is written to the writer node. The second copy is written to the same rack as the first copy, but on a different half (which can be composed of several nodes). The target node is determined by a hash value on the fileset ID of the file, or it is chosen randomly if the file does not belong to any fileset. The third copy is striped across the disks in a cyclical fashion with the restriction that no two disks are in the same failure group. The following conditions must be met while using a write affinity depth of 2 to get evenly allocated space in all disks:- The configuration in disk number, disk size, and node number for each rack must be similar.
- The number of nodes must be the same in the bottom half and the top half of each rack.
This behavior can be altered on an individual file basis by using the --write-affinity-failure-group option of the mmchattr command.
This parameter is ignored if write affinity is disabled for the storage pool.
- blockGroupFactor=BlockGroupFactor
- Specifies how many file system blocks are laid out sequentially on disk to behave like a single large block. This option only works if --allow-write-affinity is set for the data pool. This applies only to a new data block layout; it does not migrate previously existing data blocks.
See the section about File Placement Optimizer in the IBM Spectrum Scale: Administration Guide.
- -A {yes | no | automount}
- Indicates when
the file system is to be mounted:
- yes
- When the GPFS daemon starts. This is the default.
- no
- The file system is mounted manually.
- automount
- On non-Windows nodes, when the file system is first
accessed. On Windows nodes, when the GPFS daemon starts.Note: IBM Spectrum Protect™ for Space Management does not support file systems with the -A option set to automount.
- -B BlockSize
Specifies the size of data blocks in the new file system. Valid values are 64 KiB, 128 KiB, 256 KiB, 512 KiB, 1 MiB, 2 MiB, 4 MiB, 8 MiB, and 16 MiB (for IBM Spectrum Scale RAID only). Specify this value with the character K or M; for example, 512K sets the block size to 512 KiB. The subblock size is determined by the block size. Subblock size ranges from 2 KiB to 16 KiB, but for most block sizes the subblock size is 8 KiB:
Table 1. Block sizes and subblock sizes Block size Subblock size 64 KiB 2 KiB 128 KiB 4 KiB 256 KiB, 512 KiB, 1 MiB, 2 MiB, 4 MiB 8 KiB 8 MiB, 16 MiB 16 KiB - Default block size and subblock size
- The default block size depends on the file system format version of the new file system, which
is determined by the specified or default value of the --version parameter. For
more information about the --version parameter, see the description of it later
in this help topic.
- If the format version of the new file system is 5.0.0.0 or greater, then the default block size is 4 MiB
or the value of the maxblocksize attribute of the cluster,
whichever is smaller. If maxblocksize is less than 256 KiB, then
you must explicitly set -B
BlockSize to 64 KiB or 128 KiB. For more information about the
maxblocksize attribute, see mmchconfig command.
The default block size of 4 MiB provides good sequential performance, makes efficient use of disk space, and provides good performance for small files. It works well for the widest variety of workloads.
- If the format version for the new file system is less than 5.0.0.0, then the default block size is 256 KiB.
The subblock size is determined by the default block size:- If the file system format version for the new file system is 5.0.0.0 or greater, the subblock size is as shown in the preceding table, Table 1.
- If the file system format version for the new file system is less than 5.0.0.0, then the subblock size is 1/32 of the block size.
- If the format version of the new file system is 5.0.0.0 or greater, then the default block size is 4 MiB
or the value of the maxblocksize attribute of the cluster,
whichever is smaller. If maxblocksize is less than 256 KiB, then
you must explicitly set -B
BlockSize to 64 KiB or 128 KiB. For more information about the
maxblocksize attribute, see mmchconfig command.
- -D {nfs4 | posix}
- Specifies whether a deny-write open lock blocks writes, which is expected and required by NFS V4. File systems supporting NFS V4 must have -D nfs4 set. The option -D posix allows NFS writes even in the presence of a deny-write open lock. If you intend to export the file system using NFS V4 or Samba, you must use -D nfs4. For NFS V3 (or if the file system is not NFS exported at all) use -D posix. The default is -D nfs4.
- -E {yes | no}
- Specifies whether to report exact mtime values (-E yes), or to periodically update the mtime value for a file system (-E no). If it is more desirable to display exact modification times for a file system, specify or use the default -E yes.
- -i InodeSize
- Specifies the byte size of inodes. Supported inode sizes are 512, 1024, and 4096 bytes. The default is 4096.
- -j {cluster | scatter}
- Specifies the default block allocation map type to be used if layoutMap is not specified for a given storage pool.
- -k {posix | nfs4 | all}
- Specifies the type of authorization
supported by the file system:
- posix
- Traditional GPFS ACLs only (NFS V4 and Windows ACLs are not allowed). Authorization controls are unchanged from earlier releases.
- nfs4
- Support for NFS V4 and Windows ACLs only. Users are not allowed to assign traditional GPFS ACLs to any file system objects (directories and individual files).
- all
- Any supported ACL type is permitted. This includes traditional GPFS (posix) and NFS V4 and Windows ACLs (nfs4).
The administrator is allowing a mixture of ACL types. For example, fileA may have a posix ACL, while fileB in the same file system may have an NFS V4 ACL, implying different access characteristics for each file depending on the ACL type that is currently assigned. The default is -k all.
Avoid specifying nfs4 or all unless files are to be exported to NFS V4 or Samba clients, or the file system is mounted on Windows. NFS V4 and Windows ACLs affect file attributes (mode) and have access and authorization characteristics that are different from traditional GPFS ACLs.
- -K {no | whenpossible | always}
- Specifies
whether strict replication is to be enforced:
- no
- Indicates that strict replication is not enforced. GPFS tries to create the needed number of replicas, but still returns EOK as long as it can allocate at least one replica.
- whenpossible
- Indicates that strict replication is enforced provided the disk configuration allows it. If the number of failure groups is insufficient, strict replication is not enforced. This is the default value.
- always
- Indicates that strict replication is enforced.
For more information, see the topic "Strict replication" in the IBM Spectrum Scale: Problem Determination Guide.
- -L LogFileSize
- Specifies the size of the internal log files. The LogFileSize must be
a multiple of the metadata block size.
The default log file size is 32 MiB in most cases. However, if the data block size (parameter -B) is less than 512 KiB or if the metadata block size (parameter --metadata-block-size) is less than 256 KiB, then the default log file size is either 4 MiB or the metadata block size, whichever is greater.
The minimum size is 256 KiB and the maximum size is 1024 MiB. Specify this value with the K or M character, for example: 8M.
The default log size works well in most cases. An increased log file size is useful when the highly available write cache feature (parameter --write-cache-threshold) is enabled.
- -m DefaultMetadataReplicas
- Specifies the default number of copies of inodes, directories, and indirect blocks for a file. Valid values are 1, 2, and 3. This value cannot be greater than the value of MaxMetadataReplicas. The default is 1.
- -M MaxMetadataReplicas
- Specifies the default maximum number of copies of inodes, directories, and indirect blocks for a file. Valid values are 1, 2, and 3. This value cannot be less than the value of DefaultMetadataReplicas. The default is 2.
- -n NumNodes
- The estimated number of nodes that will mount the file system in the local cluster and all
remote clusters. This is used as a best guess for the initial size of some file system data
structures. The default is 32. This value can be changed after
the file system has been created but it does not change the existing data structures. Only the newly
created data structure is affected by the new value. For example, new storage
pool.
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 (For more information, see GPFS architecture ). If you are sure there will never be more than 64 nodes, 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.
- -Q {yes | no}
- Activates quotas automatically when the file system is mounted.
The default is -Q no. Issue the mmdefedquota command
to establish default quota values. Issue the mmedquota command
to establish explicit quota values.To activate GPFS quota management after the file system has been created:
- Mount the file system.
- To establish default quotas:
- Issue the mmdefedquota command to establish default quota values.
- Issue the mmdefquotaon command to activate default quotas.
- To activate explicit quotas:
- Issue the mmedquota command to activate quota values.
- Issue the mmquotaon command to activate quota enforcement.
- -r DefaultDataReplicas
- Specifies the default number of copies of each data block for a file. Valid values are 1, 2, and 3. This value cannot be greater than the value of MaxDataReplicas. The default is 1.
- -R MaxDataReplicas
- Specifies the default maximum number of copies of data blocks for a file. Valid values are 1, 2, and 3. This value cannot be less than the value of DefaultDataReplicas. The default is 2.
- -S {yes |
no
| relatime}
Controls how the file attribute atime is updated.
Note: The attribute atime is updated locally in memory, but the value is not visible to other nodes until after the file is closed. To get an accurate value of atime, an application must call subroutine gpfs_stat or gpfs_fstat.- yes
- The atime attribute is not updated. The subroutines gpfs_stat and gpfs_fstat return the time that the file system was last mounted with relatime=no. For more information, see the topics mmmount command with the -o parameter and Mount options specific to IBM Spectrum Scale.
- no
- The atime attribute is updated whenever the file is read. This option is the default if the minimum release level (minReleaseLevel) of the cluster is less than 5.0.0 when the file system is created.
- relatime
- The atime attribute is updated whenever the file is read, but only if one
of the following conditions is true:
- The current file access time (atime) is earlier than the file modification time (mtime).
- The current file access time (atime) is greater than the atimeDeferredSeconds attribute. For more information, see mmchconfig command.
- -T MountPoint
- Specifies the mount point directory of the GPFS file system. If it is not specified, the mount point is set to DefaultMountDir/Device. The default value for DefaultMountDir is /gpfs but, it can be changed with the mmchconfig command.
- -t DriveLetter
- Specifies the drive letter to use when the file system is mounted on Windows.
- -v {yes | no}
- Verifies 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, use -v no on the next invocation
of the command.Important: Using -v no on a disk that already belongs to a file system will corrupt that file system. This will not be noticed until the next time that file system is mounted.
- -z {yes | no}
- Enable or disable DMAPI on the file system. Turning this option on requires an external data
management application such as IBM Spectrum
Protect hierarchical
storage management (HSM) before the file system can be mounted. The default is -z
no.
For further information regarding DMAPI for GPFS, see GPFS-specific DMAPI events.
Note: IBM Spectrum Protect for Space Management does not support file systems with the -A option set to automount. - --filesetdf
- Specifies that when quotas are enforced for a fileset, the numbers reported by the df command are based on the quotas for the fileset (rather than the entire file system). This option affects the df command behavior only on Linux nodes.
- --nofilesetdf
- Specifies that when quotas are enforced for a fileset, the numbers reported by the df command are based on the quotas for the entire file system (rather than individual filesets. This is the default.
- --inode-limit MaxNumInodes[:NumInodesToPreallocate]
- Specifies the maximum number of files in the file system.
For file systems on which you intend to create files in parallel, if the total number of free inodes is not greater than 5% of the total number of inodes, file system access might slow down. Take this into consideration when creating your file system.
The parameter NumInodesToPreallocate specifies the number of inodes that the system immediately preallocates. If you do not specify a value for NumInodesToPreallocate, GPFS dynamically allocates inodes as needed.
You can specify the NumInodes and NumInodesToPreallocate values with a suffix, for example 100K or 2M. Note that in order to optimize file system operations, the number of inodes that are actually created may be greater than the specified value.
- --log-replicas LogReplicas
- Specifies the number of recovery log replicas. Valid values are 1,
2, 3, or DEFAULT. If
not specified, or if DEFAULT is specified, the number of log replicas is
the same as the number of metadata replicas currently in effect for the file system.
This option is applicable only if the recovery log is stored in the system.log storage pool. For more information about the system.log storage pool, see The system.log storage pool.
- --metadata-block-size MetadataBlockSize
- Specifies the block size for the system storage pool, provided its usage is set to metadataOnly. Valid values are the same as those listed for -B BlockSize.
- --perfileset-quota
- Sets the scope of user and group quota limit checks to the individual fileset level (rather than the entire file system).
- --noperfileset-quota
- Sets the scope of user and group quota limit checks to the entire file system (rather than per individual fileset). This is the default.
- --mount-priority Priority
- Controls 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.
File systems with higher Priority numbers are mounted after file systems with lower numbers. File systems that do not have mount priorities are mounted last. A value of zero indicates no priority. This is the default.
- --version VersionString
- Specifies the file system format version of the new file
system, such as 4.2.3.0. A file system format version is associated with a
file system format number (for example, 17.0) that determines the features that are enabled in the
new file system. For more information about these values, see File system format changes between versions of IBM Spectrum Scale.
If you do not specify this parameter, the file system format version of the new file system defaults to the version of IBM Spectrum Scale that is installed on the node where you issue the command. For example, if IBM Spectrum Scale version 4.2.3 is installed on the node where you issue the command, then the default file system format version for the new file system is 4.2.3.0.
Whether you specify the file system format version or let it assume the default value, the file system format version must be in the range 4.1.1.0 - mRL, where mRL is the minimum release level of the cluster (minReleaseLevel).
The file system format version also affects the default value of the -B BlockSize parameter. For more information, see the description of that parameter earlier in this help topic.
Important:- A remote node with an installed product version of IBM Spectrum Scale (for example, 4.2.3) that is less than the file system format version of the new file system (such as 5.0.0) will not be able to access the file system.
- Windows nodes can mount only file systems with a file system format version greater than or equal to 3.2.1.5.
- If you do not specify this parameter and the installed product version of the node where you issue the command is greater than the minimum release level (minReleaseLevel) of the cluster, then the command returns with an error message and prompts you to upgrade the minimum release level. To avoid this result, specify a file system format version with the --version parameter.
- In many contexts you might want to let the file system format version assume its default value.
However, specifying an explicit file system format version can be useful or necessary in the
following contexts:
- When nodes in the cluster are running different versions of IBM Spectrum Scale.
- When you want to make the file system available to remote clusters in which nodes are running an earlier version of IBM Spectrum Scale.
- --profile ProfileName
- Specifies a predefined profile of attributes to be applied. System-defined profiles are located
in /usr/lpp/mmfs/profiles/. All the file system attributes listed under a file system stanza are
changed as a result of this command. The following system-defined profile names are accepted:
- gpfsProtocolDefaults
- gpfsProtocolRandomIO
The file system attributes are applied at file system creation. If there is a current profile in place on the system (use mmlsconfig profile to check), then the file system is created with those attributes and values listed in the profile's file system stanza. The default is to use whatever attributes and values associate with the current profile setting.
Furthermore, any and all file system attributes from an installed profile file can be by-passed with '--profile=userDefinedProfile', where the userDefinedProfile is a profile file has been installed by the user in /var/mmfs/etc/.
User-defined profiles consist of the following stanzas:%cluster: [CommaSeparatedNodesOrNodeClasses:]ClusterConfigurationAttribute=Value ... %filesystem: FilesystemConfigurationAttribute=Value ...
A sample file can be found in /usr/lpp/mmfs/samples/sample.profile. See the mmchconfig command for a detailed description of the different configuration parameters.
User-defined profiles should be used only by experienced administrators. When in doubt, use the mmchconfig command instead.
- --write-cache-threshold HAWCThreshold
- Specifies the maximum length (in bytes) of write requests that will be initially buffered in the
highly-available write cache before being written back to primary storage. Only synchronous write
requests are guaranteed to be buffered in this fashion.
A value of 0 disables this feature. 64K is the maximum supported value. Specify in multiples of 4K.
This feature can be enabled or disabled at any time (the file system does not need to be unmounted). For more information about this feature, see Highly available write cache (HAWC).
Exit status
- 0
- Successful completion.
- nonzero
- A failure has occurred.
Security
You must have root authority to run the mmcrfs command.
The node on which the command is issued must be able to execute remote shell commands on any other node in the cluster without the use of a password and without producing any extraneous messages. For more information, see Requirements for administering a GPFS file system.
Examples
mmcrfs gpfs1 -F /tmp/freedisks -B 512K -m 2 -r 2 -Q yes -T /gpfs1
The system
displays output similar
to:The following disks of gpfs1 will be formatted on node c21f1n13:
hd2n97: size 1951449088 KB
hd3n97: size 1951449088 KB
hd4n97: size 1951449088 KB
Formatting file system ...
Disks up to size 16 TB can be added to storage pool 'system'.
Creating Inode File
Creating Allocation Maps
Creating Log Files
Clearing Inode Allocation Map
Clearing Block Allocation Map
Formatting Allocation Map for storage pool 'system'
19 % complete on Tue Feb 28 18:03:20 2012
42 % complete on Tue Feb 28 18:03:25 2012
62 % complete on Tue Feb 28 18:03:30 2012
79 % complete on Tue Feb 28 18:03:35 2012
96 % complete on Tue Feb 28 18:03:40 2012
100 % complete on Tue Feb 28 18:03:41 2012
Completed creation of file system /dev/gpfs1.
mmcrfs: Propagating the cluster configuration data to all
affected nodes. This is an asynchronous process.
See also
Location
/usr/lpp/mmfs/bin