ASM: ACFS Filesystem , practiced and explained.

Background:- According to documentation here

A lot more on that part in documentation,

• How about creating a database home on the ASM Diskgroups?
• How about using my asm diskgroups to store my backups or any other generic files?
• How about using my asm diskgroup as cluster filesystem like vxfs

Well the answer is ACFS!!!! Read on…

The acfs filesystem is capable of providing the generic or cluster filesystem capabilities like VCFS etc.

It supports to generic files like Oracle Homes or any other journling filesystem capabilities, remember without this only database related files are managed in the diskgroups in ASM, that restriction is lifted with help of ACFS.

What you need?

1) ADVM – ASM Dynamic Volume Manager (the module that provides by Oracle Grid infrastructure now, acfs* executables in the $GI_HOME)

“acfsload” – to start and stop the drivers

“advmutil” – to display ASM dynamic volume details

“acfsutil” – to register and unregister acfs mount points, display the “registry” contents, display acfs file system metadata and create and remove acfs snapshots.

“asmcmd” – to create and delete asm dynamic volumes, display volume metadata, list disk groups anddisplay volume statistics

2) ASMLib – ASM Library, ASM Support lib and ASM Drivers from oracle site.

3) ASM Instance

What you will learn today?

We will use ACFS filesystem as my Oracle Home, this ACFS filesystem is mounted by ASM diskgroups, facilitated by ASM Volumes, volumes created on the disk partitions added in the asm registry.

The high level steps will be:-

1) Load the ACFS driver into kernel

2) Create partitions (but do not journal them) for the newly added disks

3) Provision the partitions with ASM Lib i.e creating asm disks

4) Use ASMCA to configure the Volumes and ACFS filesystem

The asmca broadly does the following, Just in case if you want to do the same in asmcmd

1) executes volcreate

2) execute volenable

3) execute mkdg to create a diskgroup based on the volume created in step 1

4) execute mount diskgroup

5) Add the entries in fstab with acfs filesystem

6) Mount the acfsfilesystem

Let’s Practice

Step1 : Load the acfs into kernel

(assuming you have Grid Home installed and asm is running and ASM lib is loaded)

Manually load the modules required for ACFS, with the command:

/u01/app/grid/product/11.2.0/grid/bin/acfsload start -s

Step2: Create Partitions

Two new disks on my server, lets utilize those, fdisk –l reveals the same.

Create a partition layout in those two /dev/sdd, /dev/sde disks

Note:- You need to create a partitions on disk before using and recognised by ASM as a provisioned disk

Step3: Provision the disks with ASM libraries.

You can see that I have the ACFSDISK1 and ACFSDISK2 as my asm provisioned disks, DBDATA and DBHOME also.

Step 4: Use ASMCA , to add this acfs disks to my ASM instances as volumes, for that First you need to create diskgroups

a) Click on Diskgroup tab & create.

b) Provide the Diskgroup Name as ACFS

c) See, the diskgroup ACFS, DBDATA, DBHOME has been created.(the DBHOME and DBDATA is created earlier, not to be confused, please)

Now create a mount point clusterfilesystem/Volumes. Click on cluster filesystem tab and select create volume.

d) Provide the acfs Volume name, etc and also you will see two sections, the volume you are creating is for Database Home or generic filesystem etc.

e)

Now your Diskgroup created,acfs volume created and mounted and registered for next reboot. Lets check in OS.

5) Add entries in /etc/fstab for persistent mount of volumes during the reboots.

Note: Observe the filesystem mount type acfs for the line /dev/asm/* stuff , its acfs, for normal it will be ext3,

6) Mount them.

Before ACFS snap:-

After ACFS creation snap:-

I had now, /u02/acfstest as my generic filesystem and the /u02/app/oracle/product/11.2.0/db_1 as the database home (this has created as dbhome earlier on acfs only)

Below table is for your understanding more on this,

Troubleshooting:-

Sometimes the acfs volumes does not mount when the reboot happens, you may need to rely on the command line using asmcmd.

Case:- ACFS Volumes does not mount after reboot

1) Verify the asm driver and advm is loaded and running

The screenshot says advm is not running.

2) Start ADVM,

Go to Oracle Grid Home and then use acfsload start –s,

observe the advm is now loaded into kernel

3) Check the volume now in asmcmd, if not enabled let enable with volenable command

Its disabled …..

4) Lets enable it… When you enable the volume the underlying diskgroup will be mounted automatically here in this case DBHOME

Observe the mountpath, the volume device etc, same entries as like in fstab

5) Check in OS, my sqlplus is not available, as at OS level the volume is not mounted.

6) Either keeping the following lines in fstab or using mount –t with acfs filessytem will help now

/dev/asm/dbhome-314 /u02/app/oracle/product/11.2.0/db_1 acfs

or

/bin/mount –t acfs /dev/asm/dbhome-314 /u02/app/oracle/product/11.2.0/db_1

7) Verify the mounts at OS level now, my DB HOME back again, you can sqlplus and your database binaries now.

Not that too complex, but one must know about the storage and the basic unix administration in order to get along with this.

-Thanks

Geek DBA