Create memory resident filesystems (RAM disk) on AIX

AIX supports memory-resident file systems. It can be used to maximize disk performance. It’s equivalent to Solaris tmpfs filesystem.
NOTE: RAM disk doesn’t survive a reboot.

Steps to create a RAM disk on AIX:

  • Get size of real (online) memory.
  • Create the RAM disk
  • Create the file system
  • Mount the file system.

 

  • Get size of real (online) memory.
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[root@aix:/] lparstat -i|grep Memory|egrep 'Minimum|Online|Maximum'
Online Memory                              : 16384 MB
Maximum Memory                             : 24576 MB
Minimum Memory                             : 256 MB

Or,

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[root@aix:/] bootinfo -r
16777216
  • Create the RAM disk.
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[root@aix:/] mkramdisk 1024M
/dev/rramdisk0

NOTE: By default, RAM disk pages are pinned. if you want to create RAM disk pages that are not pinned use ‘-u’ flag.

  •   Create the file system.
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[root@aix:/] mkfs -V jfs2 /dev/ramdisk0
 mkfs: destroy /dev/ramdisk0 (yes)? y
   File system created successfully.
   16176 kilobytes total disk space.
   Device /dev/ramdisk0:
   Standard empty filesystem
   Size:           2096680 512-byte (DEVBLKSIZE) blocks
  • Mount the file system.
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[root@aix:/] mkdir /ramdiskfs
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[root@aix:/] mount -V jfs2 -o log=NULL /dev/ramdisk0 /ramdiskfs
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[root@aix:/] mount
  node       mounted        mounted over    vfs       date        options
-------- ---------------  ---------------  ------ ------------ ---------------
         /dev/hd4         /                jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/hd2         /usr             jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/hd9var      /var             jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/hd3         /tmp             jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/hd1         /home            jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/hd11admin   /admin           jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /proc            /proc            procfs Dec 07 09:33 rw
         /dev/hd10opt     /opt             jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/livedump    /var/adm/ras/livedump jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/syslog_lv   /var/syslog      jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/cores_lv    /CORES           jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/fslv00      /REPOS/SVN1SYNC  jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/db2inslv01  /db2inst1        jfs2   Dec 07 09:33 rw,log=/dev/loglv00
         /dev/adm_lv      /tsmadm          jfs2   Dec 07 09:33 rw,log=/dev/loglv00
         /dev/reportinlv  /reporting       jfs2   Dec 07 09:33 rw,log=/dev/loglv00
         /dev/fslv02      /powervp         jfs2   Dec 07 09:33 rw,log=/dev/hd8
         /dev/fslv03      /db2flash        jfs2   Dec 07 09:33 rw,log=/dev/loglv01
         /dev/ramdisk0    /ramdiskfs       jfs2   Feb 08 10:26 rw,log=NULL
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[root@aix:/] df -m /ramdiskfs
Filesystem    MB blocks      Free %Used    Iused %Iused Mounted on
/dev/ramdisk0   1024.00   1023.52    1%        4     1% /ramdiskfs
  • To umount, delete RAM disk follow these steps
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[root@aix:/] umount /ramdiskfs/
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[root@aix:/] rmramdisk rramdisk0

That’s it!

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