5 Configuring Oracle Real Application Clusters Storage

5.1.1 Overview of Oracle Database and Recovery File Options

There are three ways of storing Oracle Database and recovery files:

• Automatic Storage Management: Automatic Storage Management (ASM) is an integrated, high-performance database file system and disk manager for Oracle Database files. It performs striping and mirroring of database files automatically.

  Note:

  For Standard Edition Oracle Database installations using Oracle RAC, ASM is the only supported storage option.

  Only one ASM instance is permitted for each node regardless of the number of database instances on the node.

• A supported shared file system: Supported file systems include the following:

  • A supported cluster file system: Note that if you intend to use a cluster file system for your data files, then you should create partitions large enough for the database files when you create partitions for Oracle Clusterware. If you intend to store Oracle Clusterware files on OCFS2, then you must ensure that OCFS2 volume sizes are at least 500 MB each.

    See Also:

    The Certify page on OracleMetalink for supported cluster file systems

  • NAS Network File System (NFS) listed on Oracle Certify: Note that if you intend to use NFS for your data files, then you should create partitions large enough for the database files when you create partitions for Oracle Clusterware.

  See Also:

  The Certify page on OracleMetalink for supported Network Attached Storage (NAS) devices, and supported cluster file systems

• Block or Raw Devices: A partition is required for each database file. If you do not use ASM, then for new installations on raw devices, you must use a custom installation.

  Note:

  On Linux, Oracle recommends using block devices for new installations.

5.1.2 General Storage Considerations for Oracle RAC

For all installations, you must choose the storage option that you want to use for Oracle Database files, or for Oracle Clusterware with Oracle RAC. If you want to enable automated backups during the installation, then you must also choose the storage option that you want to use for recovery files (the Fast recovery area). You do not have to use the same storage option for each file type.

For single-instance Oracle Database installations using Oracle Clusterware for failover, you must use OCFS2, ASM, block devices (on Linux), or shared raw disks if you do not want the failover processing to include dismounting and remounting of local file systems.

The following table shows the storage options supported for storing Oracle Database files and Oracle Database recovery files. Oracle Database files include data files, control files, redo log files, the server parameter file, and the password file.

https://metalink.oracle.com

Use the following guidelines when choosing the storage options that you want to use for each file type:

• You can choose any combination of the supported storage options for each file type provided that you satisfy all requirements listed for the chosen storage options.

• Oracle recommends that you choose Automatic Storage Management (ASM) as the storage option for database and recovery files.

• For Standard Edition Oracle RAC installations, ASM is the only supported storage option for database or recovery files.

• You cannot use ASM to store Oracle Clusterware files, because these files must be accessible before any ASM instance starts.

• If you intend to use ASM with Oracle RAC, and you are configuring a new ASM instance, then your system must meet the following conditions:

  • All nodes on the cluster have the 11g release 1 (11.1) version of Oracle Clusterware installed.

  • Any existing ASM instance on any node in the cluster is shut down.

• If you intend to upgrade an existing Oracle RAC database, or an Oracle RAC database with ASM instances, then you must ensure that your system meets the following conditions:

  • Oracle Universal Installer (OUI) and Database Configuration Assistant (DBCA) are run on the node where the Oracle RAC database or Oracle RAC database with ASM instance is located.

  • The Oracle RAC database or Oracle RAC database with an ASM instance is running on the same nodes that you intend to make members of the new cluster installation. For example, if you have an existing Oracle RAC database running on a three-node cluster, then you must install the upgrade on all three nodes. You cannot upgrade only 2 nodes of the cluster, removing the third instance in the upgrade.

  See Also:

  Oracle Database Upgrade Guide for information about how to prepare for upgrading an existing database

• If you do not have a storage option that provides external file redundancy, then you must configure at least three voting disk areas to provide voting disk redundancy.

5.1.3 After You Have Selected Disk Storage Options

After you have installed and configured Oracle Clusterware storage, and after you have reviewed your disk storage options for Oracle Database files, you must perform the following tasks in the order listed:

1: Check for available shared storage with CVU

Refer to Checking for Available Shared Storage with CVU.

2: Configure storage for Oracle Database files and recovery files

• To use a shared file system for database or recovery file storage, refer to Configuring Storage for Oracle Database Files on a Supported Shared File System, and ensure that in addition to the volumes you create for Oracle Clusterware files, you also create additional volumes with sizes sufficient to store database files.

• To use Automatic Storage Management for database or recovery file storage, refer to "Configuring Disks for Automatic Storage Management with ASMLIB"

• To use shared devices for database file storage, refer to "Configuring Storage for Oracle Database Files on Shared Storage Devices".

  Note:

  If you choose to configure database files on raw devices, note that you must complete database software installation first, and then configure storage after installation.

  You cannot use OUI to configure a database that uses raw devices for storage. In a future release, the option to use raw and block devices for database storage will become unavailable.

5.4.1 Requirements for Using a File System for Oracle Database Files

To use a file system for Oracle Database files, the file system must comply with the following requirements:

• To use a cluster file system, it must be a supported cluster file system, as listed in the section "Deciding to Use a Cluster File System for Data Files".

• To use an NFS file system, it must be on a certified NAS device.

• If you choose to place your database files on a shared file system, then one of the following must be true:

  • The disks used for the file system are on a highly available storage device, (for example, a RAID device that implements file redundancy).

  • The file systems consist of at least two independent file systems, with the database files on one file system, and the recovery files on a different file system.

• The oracle user must have write permissions to create the files in the path that you specify.

Use Table 5-2 to determine the partition size for shared file systems.

In Table 5-2, the total required volume size is cumulative. For example, to store all database files on the shared file system, you should have at least 3.4 GB of storage available over a minimum of two volumes.

5.4.2 Deciding to Use a Cluster File System for Data Files

For Linux x86 (32-bit) and x86-64 (64-bit) platforms, Oracle provides a cluster file system, OCFS2. You can have a shared Oracle home on OCFS2.

If you have an existing Oracle installation, then use the following command to determine if OCFS2 is installed:

# /sbin/modinfo ocfs2

If you want to install the Oracle Database files on an OCFS2 file system, and the packages are not installed, then download them from the following Web site. Follow the instructions listed with the kit to install the packages and configure the file system:

OCFS2:

http://oss.oracle.com/projects/ocfs2/

https://metalink.oracle.com

5.4.3 Deciding to Use NFS for Data Files

Network-attached storage (NAS) systems use NFS to access data. You can store data files on a supported NFS system.

NFS file systems must be mounted and available over NFS mounts before you start installation. Refer to your vendor documentation to complete NFS configuration and mounting.

5.4.4 Deciding to Use Direct NFS for Datafiles

This section contains the following information about Direct NFS:

• About Direct NFS Storage

• Using the Oranfstab File with Direct NFS

• Mounting NFS Storage Devices with Direct NFS

5.4.5 Enabling Direct NFS Client Oracle Disk Manager Control of NFS

Complete the following procedure to enable Direct NFS:

1. Create an oranfstab file with the following attributes for each NFS server to be accessed using Direct NFS:

   • Server: The NFS server name.

   • Path: Up to four network paths to the NFS server, specified either by IP address, or by name, as displayed using the ifconfig command.

   • Export: The exported path from the NFS server.

   • Mount: The local mount point for the NFS server.

   Note:

   On Linux and UNIX platforms, the location of the oranfstab file is $ORACLE_HOME/dbs.

   The following is an example of an oranfstab file with two NFS server entries:

   server:  MyDataServer1
   path:  132.34.35.12
   path:  132.34.35.13
   export: /vol/oradata1 mount: /mnt/oradata1
    
   server: MyDataServer2
   path:  NfsPath1
   path:  NfsPath2
   path:  NfsPath3
   path:  NfsPath4
   export: /vol/oradata2 mount: /mnt/oradata2
   export: /vol/oradata3 mount: /mnt/oradata3
   export: /vol/oradata4 mount: /mnt/oradata4
   export: /vol/oradata5 mount: /mnt/oradata5
   

2. Oracle Database uses an ODM library, libnfsodm11.so, to enable Direct NFS. To replace the standard ODM library, $ORACLE_HOME/lib/libodm11.so, with the ODM NFS library, libnfsodm11.so, complete the following steps:

   1. Change directory to $ORACLE_HOME/lib.

   2. Enter the following commands:

      cp libodm11.so libodm11.so_stub
      ln -s libnfsodm11.so libodm11.so
      

5.4.6 Disabling Direct NFS Client Oracle Disk Management Control of NFS

Use one of the following methods to disable the Direct NFS client:

• Remove the oranfstab file.

• Restore the stub libodm11.so file by reversing the process you completed in step 2b, "Enabling Direct NFS Client Oracle Disk Manager Control of NFS"

• Remove the specific NFS server or export paths in the oranfstab file.

5.4.7 Checking NFS Mount Buffer Size Parameters for Oracle RAC

If you are using NFS, then you must set the values for the NFS buffer size parameters rsize and wsize to 32768.

If you are using Direct NFS, note that Direct NFS will not work if the backend NFS server does not support a write size (wtmax) of 32768 or greater. In that case, NFS mounts fall back to a standard kernel NFS mount path.

Update the /etc/fstab file on each node with an entry similar to the following:

nfs_server:/vol/DATA/oradata  /u02/oradata     nfs\   
rw,bg,hard,nointr,rsize=32768,wsize=32768,tcp,actimeo=0,vers=3,timeo=600

5.4.8 Creating Required Directories for Oracle Database Files on Shared File Systems

Use the following instructions to create directories for shared file systems for Oracle Database and recovery files (for example, for a RAC database).

1. If necessary, configure the shared file systems that you want to use and mount them on each node.

   Note:

   The mount point that you use for the file system must be identical on each node. Ensure that the file systems are configured to mount automatically when a node restarts.

2. Use the df -h command to determine the free disk space on each mounted file system.

3. From the display, identify the file systems that you want to use:

   File Type	File System Requirements
   Database files	Choose either: A single file system with at least 1.5 GB of free disk space. Two or more file systems with at least 1.5 GB of free disk space in total.
   Recovery files	Choose a file system with at least 2 GB of free disk space.

   
   

   If you are using the same file system for more than one type of file, then add the disk space requirements for each type to determine the total disk space requirement.

4. Note the names of the mount point directories for the file systems that you identified.

5. If the user performing installation (typically, oracle) has permissions to create directories on the disks where you plan to install Oracle Database, then DBCA creates the Oracle Database file directory, and the Recovery file directory.

   If the user performing installation does not have write access, then you must create these directories manually using commands similar to the following to create the recommended subdirectories in each of the mount point directories and set the appropriate owner, group, and permissions on them:

   • Database file directory:

     # mkdir /mount_point/oradata
     # chown oracle:oinstall /mount_point/oradata
     # chmod 775 /mount_point/oradata
     

   • Recovery file directory (Fast recovery area):

     # mkdir /mount_point/Fast_recovery_area
     # chown oracle:oinstall /mount_point/Fast_recovery_area
     # chmod 775 /mount_point/Fast_recovery_area
     

By making the oracle user the owner of these directories, this permits them to be read by multiple Oracle homes, including those with different OSDBA groups.

When you have completed creating subdirectories in each of the mount point directories, and set the appropriate owner, group, and permissions, you have completed OCFS2 or NFS configuration for Oracle Database shared storage.

5.5.1 Identifying Storage Requirements for Automatic Storage Management

To identify the storage requirements for using Automatic Storage Management, you must determine how many devices and the amount of free disk space that you require. To complete this task, follow these steps:

1. Determine whether you want to use Automatic Storage Management for Oracle Database files, recovery files, or both.

   Note:

   You do not have to use the same storage mechanism for database files and recovery files. You can use the file system for one file type and Automatic Storage Management for the other.

   If you choose to enable automated backups and you do not have a shared file system available, then you must choose Automatic Storage Management for recovery file storage.

   If you enable automated backups during the installation, you can choose Automatic Storage Management as the storage mechanism for recovery files by specifying an Automatic Storage Management disk group for the Fast recovery area. Depending on how you choose to create a database during the installation, you have the following options:

   • If you select an installation method that runs Database Configuration Assistant in interactive mode (for example, by choosing the Advanced database configuration option) then you can decide whether you want to use the same Automatic Storage Management disk group for database files and recovery files, or use different disk groups for each file type.

     The same choice is available to you if you use Database Configuration Assistant after the installation to create a database.

   • If you select an installation method that runs Database Configuration Assistant in noninteractive mode, then you must use the same Automatic Storage Management disk group for database files and recovery files.

2. Choose the Automatic Storage Management redundancy level that you want to use for the Automatic Storage Management disk group.

   The redundancy level that you choose for the Automatic Storage Management disk group determines how Automatic Storage Management mirrors files in the disk group and determines the number of disks and amount of free disk space that you require, as follows:

   • External redundancy

     An external redundancy disk group requires a minimum of one disk device. The effective disk space in an external redundancy disk group is the sum of the disk space in all of its devices.

     Because Automatic Storage Management does not mirror data in an external redundancy disk group, Oracle recommends that you select external redundancy only use only RAID or similar devices that provide their own data protection mechanisms for disk devices.

   • Normal redundancy

     In a normal redundancy disk group, to increase performance and reliability, Automatic Storage Management by default uses two-way mirroring. A normal redundancy disk group requires a minimum of two disk devices (or two failure groups). The effective disk space in a normal redundancy disk group is half the sum of the disk space in all of its devices.

     For most installations, Oracle recommends that you select normal redundancy disk groups.

   • High redundancy

     In a high redundancy disk group, Automatic Storage Management uses three-way mirroring to increase performance and provide the highest level of reliability. A high redundancy disk group requires a minimum of three disk devices (or three failure groups). The effective disk space in a high redundancy disk group is one-third the sum of the disk space in all of its devices.

     While high redundancy disk groups do provide a high level of data protection, you should consider the greater cost of additional storage devices before deciding to select high redundancy disk groups.

3. Determine the total amount of disk space that you require for the database files and recovery files.

   Use the following table to determine the minimum number of disks and the minimum disk space requirements for installing the starter database:

   Redundancy Level	Minimum Number of Disks	Database Files	Recovery Files	Both File Types
   External	1	1.15 GB	2.3 GB	3.45 GB
   Normal	2	2.3 GB	4.6 GB	6.9 GB
   High	3	3.45 GB	6.9 GB	10.35 GB

   
   

   For Oracle RAC installations, you must also add additional disk space for the Automatic Storage Management metadata. You can use the following formula to calculate the additional disk space requirements (in MB):

   15 + (2 * number_of_disks) + (126 * number_of_Automatic_Storage_Management_instances)

   For example, for a four-node Oracle RAC installation, using three disks in a high redundancy disk group, you require an additional 525 MB of disk space:

   15 + (2 * 3) + (126 * 4) = 525

   If an Automatic Storage Management instance is already running on the system, then you can use an existing disk group to meet these storage requirements. If necessary, you can add disks to an existing disk group during the installation.

   The following section describes how to identify existing disk groups and determine the free disk space that they contain.

4. Optionally, identify failure groups for the Automatic Storage Management disk group devices.

   Note:

   Complete this step only if you intend to use an installation method that runs Database Configuration Assistant in interactive mode; for example, if you intend to choose the Custom installation type or the Advanced database configuration option, then complete this step. Other installation types do not enable you to specify failure groups.

   If you intend to use a normal or high redundancy disk group, then you can further protect your database against hardware failure by associating a set of disk devices in a custom failure group. By default, each device comprises its own failure group. However, if two disk devices in a normal redundancy disk group are attached to the same SCSI controller, then the disk group becomes unavailable if the controller fails. The controller in this example is a single point of failure.

   To protect against failures of this type, you could use two SCSI controllers, each with two disks, and define a failure group for the disks attached to each controller. This configuration would enable the disk group to tolerate the failure of one SCSI controller.

   Note:

   If you define custom failure groups, then you must specify a minimum of two failure groups for normal redundancy disk groups and three failure groups for high redundancy disk groups.

5. If you are sure that a suitable disk group does not exist on the system, then install or identify appropriate disk devices to add to a new disk group. Use the following guidelines when identifying appropriate disk devices:

   • All of the devices in an Automatic Storage Management disk group should be the same size and have the same performance characteristics.

   • Do not specify more than one partition on a single physical disk as a disk group device. Automatic Storage Management expects each disk group device to be on a separate physical disk.

   • Although you can specify a logical volume as a device in an Automatic Storage Management disk group, Oracle does not recommend their use. Logical volume managers can hide the physical disk architecture, preventing Automatic Storage Management from optimizing I/O across the physical devices. They are not supported with Oracle RAC.

5.5.2 Using an Existing Automatic Storage Management Disk Group

If you want to store either database or recovery files in an existing Automatic Storage Management disk group, then you have the following choices, depending on the installation method that you select:

• If you select an installation method that runs Database Configuration Assistant in interactive mode (for example, by choosing the Advanced database configuration option), then you can decide whether you want to create a disk group, or to use an existing one.

  The same choice is available to you if you use Database Configuration Assistant after the installation to create a database.

• If you select an installation method that runs Database Configuration Assistant in noninteractive mode, then you must choose an existing disk group for the new database; you cannot create a disk group. However, you can add disk devices to an existing disk group if it has insufficient free space for your requirements.

To determine if an existing Automatic Storage Management disk group exists, or to determine if there is sufficient disk space in a disk group, you can use Oracle Enterprise Manager Grid Control or Database Control. Alternatively, you can use the following procedure:

1. View the contents of the oratab file to determine if an Automatic Storage Management instance is configured on the system:

   $ more /etc/oratab
   

   If an Automatic Storage Management instance is configured on the system, then the oratab file should contain a line similar to the following:

   +ASM2:oracle_home_path
   

   In this example, +ASM2 is the system identifier (SID) of the Automatic Storage Management instance, with the node number appended, and oracle_home_path is the Oracle home directory where it is installed. By convention, the SID for an Automatic Storage Management instance begins with a plus sign.

2. Set the ORACLE_SID and ORACLE_HOME environment variables to specify the appropriate values for the Automatic Storage Management instance that you want to use.

3. Connect to the Automatic Storage Management instance as the SYS user with SYSDBA privilege and start the instance if necessary:

   $ $ORACLE_HOME/bin/sqlplus "SYS/SYS_password as SYSDBA"
   SQL> STARTUP
   

4. Enter the following command to view the existing disk groups, their redundancy level, and the amount of free disk space in each one:

   SQL> SELECT NAME,TYPE,TOTAL_MB,FREE_MB FROM V$ASM_DISKGROUP;
   

5. From the output, identify a disk group with the appropriate redundancy level and note the free space that it contains.

6. If necessary, install or identify the additional disk devices required to meet the storage requirements listed in the previous section.

   Note:

   If you are adding devices to an existing disk group, then Oracle recommends that you use devices that have the same size and performance characteristics as the existing devices in that disk group.

5.5.3 Configuring Disks for Automatic Storage Management with ASMLIB

A disk that is configured for use with Automatic Storage Management is known as a candidate disk.

If you intend to use Automatic Storage Management for database storage for Linux, then Oracle recommends that you install the ASMLIB driver and associated utilities, and use them to configure candidate disks.

The Automatic Storage Management library driver (ASMLIB) simplifies the configuration and management of the disk devices by eliminating the need to rebind disk devices used with ASM each time the system is restarted, or to configure persistent path information in the operating system configuration files.

To use the Automatic Storage Management library driver (ASMLIB) to configure Automatic Storage Management devices, complete the following tasks.

• Installing and Configuring the ASM Library Driver Software

• Configuring Disk Devices to Use ASM Library Driver on x86 Systems

• Administering the ASM Library Driver and Disks

http://www.oracle.com/technology/tech/linux/asmlib/uln.html

configure

# /etc/init.d/oracleasm configure

enable
disable

# /etc/init.d/oracleasm enable

start
stop
restart

# /etc/init.d/oracleasm restart

createdisk

# /etc/init.d/oracleasm createdisk DISKNAME devicename

deletedisk

# /etc/init.d/oracleasm deletedisk DISKNAME

querydisk

# /etc/init.d/oracleasm querydisk {DISKNAME | devicename}

listdisks

# /etc/init.d/oracleasm listdisks

scandisks

# /etc/init.d/oracleasm scandisks

5.6.1 Planning Your Shared Storage Device Creation Strategy

Before installing the Oracle Database 11g release 1 (11.1) software with Oracle RAC, if you do not place files on ASM, then create enough partitions of specific sizes to support your database, and also leave a few spare partitions of the same size for future expansion. For example, if you have space on your shared disk array, then select a limited set of standard partition sizes for your entire database. Partition sizes of 50 MB, 100 MB, 500 MB, and 1 GB are suitable for most databases. Also, create a few very small and a few very large spare partitions that are (for example) 1 MB and perhaps 5 GB or greater in size. Based on your plans for using each partition, determine the placement of these spare partitions by combining different sizes on one disk, or by segmenting each disk into same-sized partitions.

5.6.2 Configuring Block Devices on Linux for ASM

Use the following procedure to create block device partitions:

1. Use fdisk to create disk partitions on block devices for database files.

   To configure block devices and use ASM to manage data files, create one partition for each disk comprising the whole disk, and go to the procedure in the section "Configuring Disks for Automatic Storage Management with ASMLIB".

2. On each node, create or modify a permissions file in /etc/udev/permissions.d, to change the permissions of the datafiles from default root ownership. On Asianux 2, Oracle Linux 4, and Red Hat Enterprise Linux 4, this file should be called 49-oracle.permissions, so that the kernel loads it before 50-udev.permissions. On Asianux Server 3, Oracle Linux 5, Red Hat Enterprise Linux 5, and SUSE Enterprise Server 10, this file should be called 51-oracle.permissions, so that the kernel loads it after 50-udev.permissions.

   For each partition, the contents of the xx-oracle.permissions file are as follows:

   devicepartition:oracle_db_install_owner:OSDBA:0660

   Note:

   If you prefer to use manual undo management, instead of automatic undo management, then, instead of the UNDOTBSn shared storage devices, you must create a single rollback segment tablespace (RBS) on a shared storage device partition that is at least 500 MB in size.

3. For OUI to recognize a disk partition as an ASM disk candidate, you must mark the disk by logging in as root and marking the disk partitions that you created for ASM using the following command syntax, where ASM_DISK_NAME is the name of the ASM disk group, and device_name is the name of the disk device that you want to assign to that disk group:

   /etc/init.d/oracleasm createdisk ASM_DISK_NAME device_name