Creates an Oracle ACFS file system.

Syntax and Description

mkfs -t acfs -h
mkfs [-v] [-f]-t acfs [-n name ] volume_device [-a accelerator_volume] [size]

mkfs -t acfs -h displays usage text and exits.

Table 16-3 contains the options available with the mkfs command.

Table 16-3 Options for the Linux mkfs command

Option Description

-t acfs

Specifies the type of file system on Linux. acfs designates the Oracle ACFS type.


Specifies verbose mode. The progress is displayed as the operation occurs.

-n name

Specifies the name for the file system. A name can be a maximum of 64 characters. acfsutil info fs returns the name if one was specified.


Specifies the force option. This action creates the file system even if there is an existing Oracle ACFS on the volume device, although only if the file system is dismounted. This option overwrites structures on the original file system. Use this option with caution.


Displays the usage help text and exits.


Specifies the size that the file system should consume on the named device. The quantity specified can be in units of K (kilobytes), M (megabytes), G (gigabytes), T (terabytes), or P (petabytes). If a unit is not specified, the default is bytes.

If this option is not specified, the entire device is consumed.


Specifies an existing Oracle ADVM device file that is to be formatted. This device is the primary volume.

-a accelerator_volume

Specifies a secondary Oracle ACFS accelerator volume that is used by Oracle ACFS to store critical metadata.

You can use mkfs to create the on disk structure needed for Oracle ACFS file system to be mounted. The mkfs command is the traditional Linux command used to build a file system. After mkfs runs successfully, the USAGE column in the V$ASM_VOLUME view displays ACFS. root privilege is not required. The ownership of the volume device file dictates who can run this command. Oracle ADVM volumes are created with the ASMCMD volcreate command. For information about the volcreate command, refer to "volcreate".

The minimum file system size is 200 MB. The Oracle ACFS driver must be loaded for mkfs to operate successfully.

Oracle ACFS Accelerator Volume


This feature is included starting with Oracle Database 12c Release 1 ( The feature is reserved for future use. Oracle ACFS accelerator volume currently provides no performance gain in

Use an accelerator volume to reduce the time to access the Oracle ACFS metadata log, which is located on the accelerator volume. The accelerator volume is created with the -a option with the mkfs command. The value of COMPATIBLE.ADVM must be at least to use the -a option.

Create the accelerator volume on a disk group with storage that is significantly faster than the primary volume's storage. For example, Solid State Disk (SSD) storage could be used. The size of the accelerator volume should be at least 32 MB for each node in the cluster. For example, in an eight-node cluster the recommended minimum size of the accelerator volume is 256 MB. If an accelerator volume is smaller than the recommended size, the file system can operate normally, but the full benefit of the storage accelerator may not be achieved. The minimum size of the accelerator volume is 128 MB. Oracle ADVM volumes are created with the ASMCMD volcreate command. For information about the volcreate command, refer to "volcreate".

The accelerator volume is linked to the primary volume specified with the mkfs command. When mounting a file system, only the primary volume is specified. If the accelerator volume becomes inaccessible for any reason after a file system with the volume is mounted, the file system is taken offline. Only one storage accelerator volume can be associated with an Oracle ACFS file system. After an accelerator volume is associated with a file system, the volume cannot be disassociated from the file system. The accelerator volume cannot be resized.


Before creating an Oracle ACFS file system, first determine which Oracle ADVM volume devices are available. You can use the ASMCMD volinfo command to display information about the volumes and volume devices.

ASMCMD [+] > volinfo -a
         Volume Name: VOLUME1
         Volume Device: /dev/asm/volume1-123
         State: ENABLED

For information about the volcreate and volinfo commands, refer to Managing Oracle ADVM with ASMCMD .

Next create an Oracle ACFS file system on a volume device file.

Example 16-2 Using the mkfs command

$ /sbin/mkfs -t acfs /dev/asm/volume1-123

$ /sbin/mkfs -t acfs /dev/asm/volume1-127 -a /dev/asm/volume2-130