Thursday, September 03, 2009

ASM Dynamic Volume Manager and ASM Clustered File System

Two of the top features in 11gR2 are the ASM Dynamic Volume Manager (ADVM) and ASM Clustered File System (ACFS). What is the big deal about these two?

ADVM allows you to create a volume from an ASM diskgroup. Here is an example where we created a volume called asm_vol1 of 100 MB on a diskgroup called DATA:


ASMCMD [+] > volcreate -G DATA -s 100M asm_vol1


Internally it issues the command


alter diskgroup DATA add volume 'asm_vol1' size 100M;


Now you enable the volume you just created:


ASMCMD [+] > volenable -G DATA asm_vol1


Internally it issues:
alter diskgroup DATA enable volume 'asm_vol1';


You can perform other commands like resize, delete, disable; but more on that later on a full length article.

Now that the volume is created, what can you do with it. Well, like all volumes, you can create a filesystem on it. Here is an example of creating a FS called acfs1:


[root@oradba2 ~]# mkdir /acfs1
[root@oradba2 ~]# /sbin/mkfs -t acfs /dev/asm/asm_vol1-207
mkfs.acfs: version = 11.2.0.1.0.0
mkfs.acfs: on-disk version = 39.0
mkfs.acfs: volume = /dev/asm/asm_vol1-207
mkfs.acfs: volume size = 268435456


Register MountPoint Command:


[root@oradba2 ~]# /sbin/acfsutil registry -a -f /dev/asm/asm_vol1-207 /acfs1
acfsutil registry: mount point /acfs1 successfully added to Oracle Registry


If you get an error, use the force option:


[root@oradba2 /]# /sbin/mkfs.acfs -f /dev/asm/asm_vol1-207
mkfs.acfs: version = 11.2.0.1.0.0
mkfs.acfs: on-disk version = 39.0
mkfs.acfs: volume = /dev/asm/asm_vol1-207
mkfs.acfs: volume size = 268435456
mkfs.acfs: Format complete.



Now you mount the the filesystem:


[root@oradba2 /]# /bin/mount -t acfs /dev/asm/asm_vol1-207 /acfs1


Now if you will check the filesystem, you will notice a new one - /acfs1


[root@oradba2 /]# df -k
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
149313708 22429752 119176924 16% /
/dev/sda1 101086 11765 84102 13% /boot
tmpfs 907628 591640 315988 66% /dev/shm
/dev/asm/asm_vol1-207
262144 37632 224512 15% /acfs1


This new filesystem is actually carved out of the ASM diskspace. This can be used as a regular filesystem:


[root@oradba2 /]# cd /acfs1
[root@oradba2 acfs1]# ls
lost+found
[root@oradba2 acfs1]# touch 1


So, what't the big deal about it? Plenty.

First, this is part of the ASM management; so all the bells and whistles of ASM - such as asynch i/o, etc. - applies to this filesystem.

Second, this is now a "cluster" filesystem; it is visible across a cluster. So, now you have a fully functional generic filesystem visible across the cluster.

Third, this is now protected by the Grid infrastructure, if you have installed it. Remember from my earlier posts that in 11gR2 you can now have a restartable grid infrastructure even on a single instance.

More on ASM Dynamic Volume Manager later in a full length article. But I hope this makes you really interested.

22 comments:

Emre Baransel said...

Hi Arup;
Thanks for this "quick" information about 11gR2 features ADVM and ACFS. At first look, i think this may be a good option for binary installations on cluster systems. What you think about this new feature's usage?

Surachart Opun said...

thank you...

helpful me to test about it... 11gR2 features ADVM and ACFS.

Anonymous said...

Thanks for the information

I am planning to create setup of 4 servers.
I Installed two servers with oracle RAC & remaining 2 servers with in-house application.

I created the acfs file system and mounted. so i can share files between two database servers.

The requirement is, application servers can also access the same file.. what the configuration required if i will use NFS Client in application servers ?

-sumit-

Unknown said...

thanks. you may also try the sql server recover program, it quickly parses corrupted files of specified format and retrieves the source data from affected documents when possible. It may become a good addition to other ways of keeping your data safe

Unknown said...

As per Oracle Document, Volume extent is created based on the disk group AU.By Default 1M AU has
Volume extent=64M

What is the value of Volume Extent if the DiskGroup is create with 2M or more.

Robert Freeman said...

One note.... If you are using Exadata, ASM DVM is not currently supported.

Debbie J said...

ASM Cluster file system ACFS is new in Oracle 11g Release 2. ACFS is intended as a general files system accessible by the standard OS utilities.Your info helped me thanks.

Anonymous said...

Thank you for your effort..

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