ASM Filter Driver (ASMFD)


ASM Filter Driver is a Linux kernel module introduced in 12c R1. It resides in the I/O path of the Oracle ASM disks providing the following features:

  • Rejecting all non-Oracle I/O write requests to ASM Disks.
  • Device name persistency.
  • Node level fencing without reboot.


In 12c R2 ASMFD can be enabled from the GUI interface of the Grid Infrastructure installation, as shown on this post GI 12c R2 Installation at the step #8 “Create ASM Disk Group”.

Once ASM Filter Driver is in use, similarly to ASMLib the disks are managed using the ASMFD Label Name.


Here few examples about the implementation of ASM Filter Driver.

--How to create an ASMFD label in SQL*Plus
SQL> Alter system label set 'DATA1' to '/dev/mapper/mpathak';

System altered.

--How to create an ASM Disk Group with ASMFD
ATTRIBUTE 'SECTOR_SIZE'='512','LOGICAL_SECTOR_SIZE'='512','compatible.asm'='',

Diskgroup created.


ASM Filter Driver can also be managed from the ASM command line utility ASMCMD

--Check ASMFD status
ASMCMD> afd_state
ASMCMD-9526: The AFD state is 'LOADED' and filtering is 'ENABLED' on host 'oel7node06.localdomain'

--List ASM Disks where ASMFD is enabled
ASMCMD> afd_lsdsk
Label                    Filtering                Path
DATA1                      ENABLED                /dev/mapper/mpathak
DATA2                      ENABLED                /dev/mapper/mpathan
DATA3                      ENABLED                /dev/mapper/mpathw
DATA4                      ENABLED                /dev/mapper/mpathac
GIMR1                      ENABLED                /dev/mapper/mpatham
GIMR2                      ENABLED                /dev/mapper/mpathaj
GIMR3                      ENABLED                /dev/mapper/mpathal
GIMR4                      ENABLED                /dev/mapper/mpathaf
GIMR5                      ENABLED                /dev/mapper/mpathai
RECO3                      ENABLED                /dev/mapper/mpathy
RECO1                      ENABLED                /dev/mapper/mpathab
RECO2                      ENABLED                /dev/mapper/mpathx

--How to remove an ASMFD label in ASMCMD
ASMCMD> afd_unlabel DATA4





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