AUTOMATIC STORAGE MANAGEMENT (ASM)
Automatic Storage Management (ASM)
is a concept to administer Oracle related files by efficiently referencing
disks as raw devices or by using the ASMLib software. This article presents the
setup details for using either raw devices or ASMLib.
The ASM functionality is an
extention of the Oracle Managed Files (OMF) functionality.It includes striping
and mirroring to provide storage solutions with high level of redundancy. To
use ASM functionality we need to configure an ASM instance(which is apparently
not a full database instance,but just the memory structures).
In summary ASM provides the
following functionality:
* Manages groups of disks, called
disk groups.
* Manages disk redundancy within a disk group.
* Provides near-optimal I/O balancing without any manual tuning.
* Enables management of database objects without specifying mount points and
filenames.
* Supports large files.
The ASM instance shares the Oracle
home with the database instance. If you plan on running multiple database
instances on the server the ASM instance should be installed in a separate
Oracle home.
ASM can be configured using two
methods of creating disks:
a) Using asmlib
b) Using rawdevices.
Before we proceed with the
installation/configuration of ASM,it is always better to skid through the below
contents,and make yourself aware of the same:
1) DISK PARITIONING:
A) To check the paritions
available on your machine,use the command –> fdisk -l
B) To parition the current
available filesystem,follow the below:
# fdisk /dev/sda
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF
disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won’t be recoverable.
The number of cylinders for this
disk is set to 1305.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0×0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1305, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-1305, default 1305):
Using default value 1305
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read
partition table.
Syncing disks.
#
c) To delete a current existing
partition,use the below
fdisk /dev/sda
and then option “d”
2) RAW DEVICES:
It is important that if you use
raw devices,then you are required to register the raw devices in
/etc/sysconfig/rawdevices file ,and then you start the raw devices.
Edit the /etc/sysconfig/rawdevices
file, adding the following lines.
/dev/raw/raw1 /dev/sda1
/dev/raw/raw2 /dev/sda2
/dev/raw/raw3 /dev/sda3
NOTE: Ensure that df -h ,won’t
show up the above devices.If they are mounted,then these devices can’t be used
to create an ASM Instance.
Once,you edit the
/etc/sysconfig/rawdevices file,then you can start/enable/stop/disable your
rawdevices using the following command:
service rawdevices restart
3) ASM Logs:
Logfile location to monitor issues
while ASM creation –> /var/log/oracleasm
*oracleasm is the filename
–> Now that we made ourselves
aware of few commands required while creating an ASM instance.Let us proceed
with ASM instance creation.
PARTITION DISKS
Both ASMLib and raw devices
require the candidate disks to be partitioned before they can be accessed.
Example:
# ls sd*
sda sda1 sda2 sdb sdc sdd
# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF
disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won’t be recoverable.
The number of cylinders for this
disk is set to 1305.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0×0000 of partition table 4 will be corrected by w(rite)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1305, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-1305, default 1305):
Using default value 1305
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read
partition table.
Syncing disks.
#
The remaining disks (“/dev/sdc” and “/dev/sdd”) must be partitioned in the same
way.
NOTE : Ensure that after
paritioning you use either asmlib to create disks or create rawdevices and
assign them as ASM disks later using DBCA.
ASMLIB INSTALLATION
This step is only necessary if you
want to use ASMLib to access the ASM disks.
Determine your kernel version
using the following command as the root user.
# uname -r
2.6.9-34.ELsmp
#
Download the ASMLib software from the OTN website, making sure you pick the
version that matches your distribution, kernel and architecture. For this
example I used CentOS 4.3, so the following packages were required:
• oracleasm-support-2.0.1-1.i386.rpm
• oracleasmlib-2.0.1-1.i386.rpm
• oracleasm-2.6.9-34.ELsmp-2.0.1-1.i686.rpm
Install the packages as the root user.
#Install the packages with the
below commands:
rpm -Uvh
oracleasm-support-2.0.1-1.i386.rpm
rpm -Uvh oracleasmlib-2.0.1-1.i386.rpm
rpm -Uvh oracleasm-2.6.9-34.ELsmp-2.0.1-1.i686.rpm
#To check what packages/drivers
are installed on your system, use the below command:
rpm –qa | grep –i oracleasm
With the software installed,
configure the ASM kernel module.
# /etc/init.d/oracleasm configure
Configuring the Oracle ASM library driver.
This will configure the on-boot
properties of the Oracle ASM library
driver. The following questions will determine whether the driver is
loaded on boot and what permissions it will have. The current values
will be shown in brackets (‘[]‘). Hitting without typing an
answer will keep that current value. Ctrl-C will abort.
Default user to own the driver
interface []: oracle
Default group to own the driver interface []: oinstall
Start Oracle ASM library driver on boot (y/n) [n]: y
Fix permissions of Oracle ASM disks on boot (y/n) [y]:
Writing Oracle ASM library driver configuration: [ OK ]
Creating /dev/oracleasm mount point: [ OK ]
Loading module “oracleasm”: [ OK ]
Mounting ASMlib driver filesystem: [ OK ]
Scanning system for ASM disks: [ OK ]
#
Once the kernel module is loaded, stamp (or label) the partitions created
earlier as ASM disks.
# /etc/init.d/oracleasm createdisk
VOL1 /dev/sda1
Marking disk “/dev/sdb1″ as an ASM disk: [ OK ]
# /etc/init.d/oracleasm createdisk VOL2 /dev/sdb1
Marking disk “/dev/sdc1″ as an ASM disk: [ OK ]
# /etc/init.d/oracleasm createdisk VOL3 /dev/sdc1
Marking disk “/dev/sdd1″ as an ASM disk: [ OK ]
#
If this were a RAC installation, the disks would only be stamped by one node.
The other nodes would just scan for the disks.
# /etc/init.d/oracleasm scandisks
Scanning system for ASM disks: [ OK ]
#
The stamped disks are listed as follows.
# /etc/init.d/oracleasm listdisks
VOL1
VOL2
VOL3
#
The disks are now ready to be used by ASM.
To administer the Automatic
Storage Management library driver and disks, use the oracleasm initialization
script with different options, as follows:
# /etc/init.d/oracleasm configure
# /etc/init.d/oracleasm enable
# /etc/init.d/oracleasm restart
# /etc/init.d/oracleasm createdisk
DISKNAME devicename
# /etc/init.d/oracleasm deletedisk
DISKNAME
Caution: Do not use this command to unmark disks that are being used by an
Automatic Storage Management disk group. You must drop the disk from the
Automatic Storage Management disk group before you unmark it.
querydisk
Use the querydisk option to
determine whether a disk device or disk name is being used by the Automatic
Storage Management library driver:
# /etc/init.d/oracleasm querydisk {DISKNAME | devicename}
listdisks
Use the listdisks option to list the disk names of marked Automatic Storage
Management library driver disks:
# /etc/init.d/oracleasm listdisks
scandisks
Use the scandisks option to enable cluster nodes to identify which shared disks
have been marked as Automatic Storage Management library driver disks on
another node:
# /etc/init.d/oracleasm scandisks
Raw Device Setup
This step is only necessary if you
want ASM to access the disks as raw devices.
Edit the /etc/sysconfig/rawdevices
file, adding the following lines.
/dev/raw/raw1 /dev/sda1
/dev/raw/raw2 /dev/sdb1
/dev/raw/raw3 /dev/sdc1
Restart the rawdevices service using the following command.
root@localhost ~]# service
rawdevices restart
Assigning devices:
/dev/raw/raw1 –> /dev/sda1
/dev/raw/raw1: bound to major 8, minor 3
/dev/raw/raw2 –> /dev/sdb1
/dev/raw/raw2: bound to major 8, minor 7
/dev/raw/raw3 –> /dev/sdc1
/dev/raw/raw3: bound to major 8, minor 8
done
[root@localhost ~]#
Run the following commands and add
them the /etc/rc.local file.
chown oracle:oinstall
/dev/raw/raw1
chown oracle:oinstall /dev/raw/raw2
chown oracle:oinstall /dev/raw/raw3
chmod 600 /dev/raw/raw1
chmod 600 /dev/raw/raw2
chmod 600 /dev/raw/raw3
The ASM raw device disks are now
configured.
ASM CREATION:
Creation of the ASM instance is
the same, regardless of the use of ASMLib or raw devices. When using ASMLib,
the candidate disks are listed using the stamp associated with them, while the
raw devices are listed using their device name.
To configure an ASM instance,
start the Database Configuration Assistant by issuing the “./runInstaller”
command as the oracle user. On the “Welcome” screen, click the “Next” button.
Select the “Advanced
Installation”, then click the “Next” Button.
Select the “Configure Automatic
Storage Management” option, then click the “Next” Button.
On the next page, when using raw
devices, the candidate discs are listed using the device names. So check the
devices and redundancy (High, normal and external) as per your requirement.
click on “change disk discovery path”
and search with string –> /dev/raw/* (Only for linux)
On the “ASM Disk Groups” screen.
Click the “Finish” button.
Click the “Yes” button to perform
another operation.
You are now ready to create a
database instance using ASM.
ASM Instance creation:
After you configure the kernel
parameters and Bash profile, performing the following.
$ export ORACLE_SID=+ASM
$ sqlplus / as sysdba
SQL*Plus: Release 10.2.0.1.0 –
Production on Sat Jul 6 14:01:06 2011
Copyright (c) 1982, 2005, Oracle.
All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 – Production
With the Partitioning, OLAP and Data Mining options
SQL> alter system register;
System altered.
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 –
Pr oduction
With the Partitioning, OLAP and Data Mining options
$
DATABASE CREATION:
Go back to the DBCA and create a
custom database in the normal way, selecting the “Automatic Storage Management
(ASM)” storage option.
· Enter the ASM password if
prompted, then click the “OK” button.
· Select the “DATA” disk group,
then clicking the “Next” button.
· Accept the default
“Oracle-Managed Files” database location by clicking the “Next” button.
· Enable the “Flash Recovery Area”
and Archiving, using the “+DATA” disk group for both.
Continue with the rest of the
DBCA, selecting the required options along the way.
To create an ASM instance first create a file called init+ASM.ora in the /tmp
directory containing the following information.
INSTANCE_TYPE=ASM
Next, using SQL*Plus connect to
the ide instance.
export ORACLE_SID=+ASM
sqlplus / as sysdba
Create an spfile using the
contents of the init+ASM.ora file.
SQL> CREATE SPFILE FROM
PFILE=’/tmp/init+ASM.ora’;
File created.
Finally, start the instance with
the NOMOUNT option.
SQL> startup nomount
ASM instance started
Total System Global Area 125829120
bytes
Fixed Size 1301456 bytes
Variable Size 124527664 bytes
Database Buffers 0 bytes
Redo Buffers 0 bytes
SQL>
The ASM instance is now ready to
use for creating and mounting disk groups. To shutdown the ASM instance issue
the following command.
SQL> shutdown
ASM instance shutdown
SQL>
Once an ASM instance is present
disk groups can be used for the following parameters in database instances
(INSTANCE_TYPE=RDBMS) to allow ASM file creation:
* DB_CREATE_FILE_DEST
* DB_CREATE_ONLINE_LOG_DEST_n
* DB_RECOVERY_FILE_DEST
* CONTROL_FILES
* LOG_ARCHIVE_DEST_n
* LOG_ARCHIVE_DEST
* STANDBY_ARCHIVE_DEST
Refference:
