2 Preparing Your Cluster

About Hardware Requirements

Each node that you want to make part of your Oracle Clusterware, or Oracle Clusterware and Oracle RAC installation, must satisfy the minimum hardware requirements of the software. These hardware requirements can be categorized as follows:

• Physical memory (at least 1.5 gigabyte (GB) of RAM)

• An amount of swap space equal the amount of RAM

• Temporary space (at least 1 GB) available in /tmp

• A processor type (CPU) that is certified with the version of the Oracle software being installed

• At minimum of 1024 x 786 display resolution, so that Oracle Universal Installer (OUI) displays correctly

• All servers that will be used in the cluster have the same chip architecture, for example, all 32-bit processors or all 64-bit processors

• Disk space for software installation locations

  You will need at least 4.5 GB of available disk space for the Grid home directory, which includes both the binary files for Oracle Clusterware and Oracle Automatic Storage Management (Oracle ASM) and their associated log files, and at least 4 GB of available disk space for the Oracle Database home directory.

  Note:

  Refer to the Oracle Grid Infrastructure Installation Guide and the Oracle Real Application Clusters Installation Guide for your operating system for the actual disk space requirements. The amount of disk space used by the Oracle software can vary, and might be higher than what is listed in this guide.

• Shared disk space

  An Oracle RAC database is a shared everything database. All data files, control files, redo log files, and the server parameter file (SPFILE) used by the Oracle RAC database must reside on shared storage that is accessible by all the Oracle RAC database instances. The Oracle RAC installation that is described in this guide uses Oracle ASM for the shared storage for Oracle Clusterware and Oracle Database files.

  Oracle Clusterware achieves superior scalability and high availability by using the following components:

  • Voting disk–Manages cluster membership and arbitrates cluster ownership between the nodes in case of network failures. The voting disk is a file that resides on shared storage. For high availability, Oracle recommends that you have more than one voting disk, and that you have an odd number of voting disks. If you define a single voting disk, then use mirroring at the file system level for redundancy.

  • Oracle Cluster Registry (OCR)–Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR contains information such as which database instances run on which nodes and which services run on which databases. The OCR also stores information about processes that Oracle Clusterware controls. The OCR resides on shared storage that is accessible by all the nodes in your cluster. Oracle Clusterware can multiplex, or maintain multiple copies of, the OCR and Oracle recommends that you use this feature to ensure high availability.

  Note:

  If you choose not to use Oracle ASM for storing your Oracle Clusterware files, then both the voting disks and the OCR must reside on a cluster file system that you configure before you install Oracle Clusterware in the Grid home.

  These Oracle Clusterware components require the following disk space on a shared file system:

  • Three Oracle Clusterware Registry (OCR) files, 280 MB each, or 840 MB total disk space

  • Three voting disk files, 280 MB each, or 840 MB total disk space

  If you are not using Oracle ASM for storing Oracle Clusterware files, then for best performance and protection, you should use multiple disks, each using a different disk controller for voting disk file placement. Ensure that each voting disk is configured so that it does not have share any hardware device or have a single point of failure.

About Network Hardware Requirements

An Oracle RAC cluster comprises two or more nodes that are linked by a private interconnect. The interconnect serves as the communication path between nodes in the cluster. Each cluster database instance uses the interconnect for messaging to synchronize the use of shared resources by each instance. Oracle RAC also uses the interconnect to transmit data blocks that are shared between the instances.

Oracle Clusterware requires that you connect the nodes in the cluster to a private network by way of a private interconnect. The private interconnect is a separate network that you configure between cluster nodes. The interconnect used by Oracle RAC is the same interconnect that Oracle Clusterware uses. This interconnect should be a private interconnect, meaning it is not accessible to nodes that are not members of the cluster.

When you configure the network for Oracle RAC and Oracle Clusterware, each node in the cluster must meet the following requirements:

• Each node has at least two network interface cards (NIC), or network adapters. One adapter is for the public network interface and the other adapter is for the private network interface (the interconnect). Install additional network adapters on a node if that node meets either of the following conditions:

  • Does not have at least two network adapters

  • Has two network interface cards but is using network attached storage (NAS). You should have a separate network adapter for NAS.

    Note:

    For the most current information about supported network protocols and hardware for Oracle RAC installations, refer to the Certify pages on My Oracle Support (formerly OracleMetaLink), which is located at

    https://metalink.oracle.com
    

• Public interface names must be the same for all nodes. If the public interface on one node uses the network adapter eth0, then you must configure eth0 as the public interface on all nodes.

• You should configure the same private interface names for all nodes as well. If eth1 is the private interface name for the first node, then eth1 should be the private interface name for your second node.

• The network adapter for the public interface must support TCP/IP.

• The network adapter for the private interface must support the user datagram protocol (UDP) using high-speed network adapters and a network switch that supports TCP/IP (Gigabit Ethernet or better).

  Note:

  You must use a switch for the interconnect. Oracle recommends that you use a dedicated network switch. Token-rings or crossover cables are not supported for the interconnect.

• For the private network, the end points of all designated interconnect interfaces must be completely reachable on the network. Every node in the cluster should be able to connect to every private network interface in the cluster.

• The host name of each node must conform to the RFC 952 standard, which permits alphanumeric characters. Host names using underscores ("_") are not allowed.

About IP Address Requirements

When performing an advanced installation of the Oracle grid infrastructure software, you can chose to use Grid Naming Service (GNS) and Dynamic Host Configuration Protocol (DHCP) for virtual IPs (VIPs). Grid Naming Service is a new feature in Oracle Database 11g release 2 that uses multicast Domain Name Server (mDNS) to enable the cluster to assign host names and IP addresses dynamically as nodes are added and removed from the cluster, without requiring additional network address configuration in the domain name server (DNS). For more information about GNS, refer to Oracle Grid Infrastructure Installation Guide for Linux.

This guide documents how to perform a typical installation, which does not use GNS. You must configure the following addresses manually in your corporate DNS:

• A public IP address for each node

• A virtual IP address for each node

• Three single client access name (SCAN) addresses for the cluster

During installation a SCAN for the cluster is configured, which is a domain name that resolves to all the SCAN addresses allocated for the cluster. The IP addresses used for the SCAN addresses must be on the same subnet as the VIP addresses. The SCAN must be unique within your network. The SCAN addresses should not respond to ping commands before installation.

During installation of the Oracle grid infrastructure, a listener is created for each of the SCAN addresses. Clients that access the Oracle RAC database should use the SCAN or SCAN address, not the VIP name or address. If an application uses a SCAN to connect to the cluster database, the network configuration files on the client computer do not need to be modified when nodes are added to or removed from the cluster. The SCAN and its associated IP addresses provide a stable name for clients to use for connections, independent of the nodes that make up the cluster. Clients can connect to the cluster database using the easy connect naming method and the SCAN.

Verifying Operating System and Software Requirements

Refer to the Oracle Grid Infrastructure Installation Guide and the Oracle Real Application Clusters Installation Guide for your platform for information about exact requirements. These requirements can include any of the following:

• The operating system version

• The kernel version of the operating system

• Modifying the values for kernel parameters

• Installed packages, patches, or patch sets

• Installed compilers and drivers

• Web browser type and version

• Additional application software requirements

If you are currently running an operating system version that is not supported by Oracle Database 11g release 2 (11.2), then you must first upgrade your operating system before installing Oracle Real Application Clusters 11g.

If you are using Oracle Enterprise Linux as your operating system, then you can use the Oracle Validated RPM system configuration script to configure your system.

To determine if the operating system requirements for Oracle Enterprise Linux have been met:

1. To determine which distribution and version of Linux is installed, run the following command at the operating system prompt as the root user:

   # cat /proc/version
   

2. To determine which chip architecture each server is using and which version of the software you should install, run the following command at the operating system prompt as the root user:

   # uname -m
   

   This command displays the processor type. For a 64-bit architecture, the output would be "x86_64".

3. To determine if the required errata level is installed, use the following procedure as the root user:

   # uname -r
   2.6.9-55.0.0.0.2.ELsmp
   

   Like most software, the Linux kernel is updated to fix bugs in the operating system. These kernel updates are referred to as erratum kernels or errata levels.

   The output in the previous example shows that the kernel version is 2.6.9, and the errata level (EL) is 55.0.0.0.2.ELsmp. Review the required errata level for your distribution. If the errata level is below the required minimum errata level, then install the latest kernel update for your operating system. The kernel updates are available from your operating system vendor.

4. To ensure there are no operating system issues affecting installation, make sure you have installed all the operating system patch updates and packages that are listed in Oracle Clusterware and Oracle Real Application Clusters Installation Guide for your platform. If you are using Oracle Enterprise Linux, you can determine if the required packages, or programs that perform specific functions or calculations, are installed by using the following command as the root user:

   # rpm -q package_name
   

   The variable package_name is the name of the package you are verifying, such as setarch. If a package is not installed, then install it from your Linux distribution media or download the required package version from your Linux vendor's Web site.

   You can also use either up2date or YUM (Yellow dog Updater Modified) to install packages and their dependencies on some Linux systems. YUM uses repositories to automatically locate and obtain the correct RPM packages for your system.

About Operating System Users and Groups

Depending on whether or not this is the first time Oracle software is being installed on this server, you may need to create operating system groups.

ORACLE_HOME=/u01/app/grid; export ORACLE_HOME

Configuring Operating System Users and Groups

In this guide, a single software owner will be used for all installations, named oracle. The oracle user will belong to the oinstall and dba operating system groups.

To create one software owner with all operating system-authenticated administration privileges:

1. Determine the groups that already exist on your server by listing the contents of the /etc/group file.

   cat /etc/group
   

2. If this is the first time Oracle software has been installed on your server, and the Oracle Inventory group does not exist, then create the Oracle Inventory group (oinstall) with a group ID that is currently not in use on all the nodes in your cluster. Enter a command as the root user that is similar to the following:

   # /usr/sbin/groupadd -g 1000 oinstall
   

3. Create an OSDBA (dba) group with a group ID that is currently not in use on all the nodes in your cluster by entering a command as the root user that is similar to the following:

   # /usr/sbin/groupadd -g 1001 dba
   

4. If the user that owns the Oracle software (oracle) does not exist on your server, you must create the user. Select a user ID (UID) that is currently not in use on all the nodes in your cluster. To determine which users have already been created on your server, list the contents of the /etc/passwd file using the command:

   cat /etc/passwd
   

   The following command shows how to create the oracle user and the user's home directory (/home/oracle) with the default group as oinstall and the secondary group as dba, using a UID of 1100:

   # useradd -u 1100 –g oinstall -G dba -d /home/oracle -r oracle
   

5. Set the password for the oracle account using the following command. Replace password with your own password.

   passwd oracle
   
   Changing password for user oracle.
   New UNIX password: password 
   retype new UNIX password: password
   passwd:  all authentication tokens updated successfully.
   

6. Repeat Step 1 through Step 5 on each node in your cluster.

7. Verify that the attributes of the user oracle are identical on each node of your cluster:

   id oracle 
   

   The command output should be similar to the following:

   uid=1100(oracle) gid=1000(oinstall) groups=1000(oinstall),1001(dba)
   

Configuring Secure Shell

To install Oracle software, Secure Shell (SSH) connectivity must be set up between all cluster member nodes. OUI uses the ssh and scp commands during installation to run remote commands on and copy files to the other cluster nodes. You must configure SSH so that these commands do not prompt for a password. SSH is also used by the configuration assistants, Enterprise Manager, and when adding nodes to the cluster.

You can configure SSH from the Oracle Universal Installer (OUI) interface during installation for the user account running the installation. The automatic configuration creates passwordless SSH connectivity between all cluster member nodes.

To enable the script to run, you must remove stty commands from the profiles of any Oracle software installation owners, and remove other security measures that are triggered during a login, and that generate messages to the terminal. These messages, mail checks, and other displays prevent Oracle software installation owners from using the SSH configuration script that is built into the Oracle Universal Installer. If they are not disabled, then SSH must be configured manually before an installation can be run.

On Linux systems, to enable Oracle Universal Installer to use the ssh and scp commands without being prompted for a pass phrase, you must have user equivalency in the cluster. User equivalency exists in a cluster when the following occurs on all nodes in the cluster:

• A given user has the same user name, user ID (UID), and password.

• A given user belongs to the same groups.

• A given group has the same group ID (GID).

For information on configuring user equivalency, see "Configuring Operating System Users and Groups".

About Configuring the Software Owner's Shell Environment

On Oracle Enterprise Linux, you run Oracle Universal Installer (OUI) from the oracle account. Oracle Universal Installer obtains information from the environment variables configured for the oracle user. Prior to running OUI, you must make the following changes to the Oracle grid infrastructure software owner's shell startup file:

• Set the default file mode creation mask (umask) of the installation user (oracle) to 022 in the shell startup file. Setting the mask to 022 ensures that the user performing the software installation creates files with 644 permissions.

• Set ulimit settings for file descriptors (nofile) and processes (nproc) for the installation user (oracle)

• Set the software owner's environment variable DISPLAY environment variables in preparation for the Oracle grid infrastructure installation

• Remove any lines in the file that set values for ORACLE_SID, ORACLE_HOME, or ORACLE_BASE environment variables.

After you have saved your changes, run the shell startup script to configure the environment.

Also, if the /tmp directory has less than 1 GB of available disk space, but you have identified a different, non-shared file system that has at least 1 GB of available space, you can set the TEMP and TMPDIR environment variables to specify the alternate temporary directory on this file system.

To review your current environment settings, use the env | more command as the oracle user.

Refer to the Oracle Clusterware Installation Guide for your platform for more information on how to configure the Oracle software owner environment prior to installation.

Verifying the Network Configuration

After you have configured the network, perform verification tests to make sure it is configured properly. If there are problems with the network connection between nodes in the cluster, the Oracle Clusterware installation will fail.

To verify the network configuration on a two-node cluster that is running Oracle Enterprise Linux:

1. As the root user, verify the configuration of the public and private networks. Verify that the interfaces are configured on the same network (either private or public) on all nodes in your cluster.

   In this example, eth0 is used for the public network and eth1 is used for the private network on each node.

   # /sbin/ifconfig
    
   eth0      Link encap:Ethernet  HWaddr 00:0E:0C:08:67:A9  
             inet addr: 192.0.2.100   Bcast:192.0.2.255   Mask:255.255.240.0
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:270332689 errors:0 dropped:0 overruns:0 frame:0
             TX packets:112346591 errors:2 dropped:0 overruns:0 carrier:2
             collisions:202 txqueuelen:1000 
             RX bytes:622032739 (593.2 MB)  TX bytes:2846589958 (2714.7 MB)
             Base address:0x2840 Memory:fe7e0000-fe800000 
    
   eth1      Link encap:Ethernet  HWaddr 00:04:23:A6:CD:59  
             inet addr: 10.10.10.11   Bcast: 10.10.10.255   Mask:255.255.240.0   
             UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
             RX packets:21567028 errors:0 dropped:0 overruns:0 frame:0
             TX packets:15259945 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:1000 
             RX bytes:4091201649 (3901.6 MB)  TX bytes:377502797 (360.0 MB)
             Base address:0x2800 Memory:fe880000-fe8a0000 
    
   lo        Link encap:Local Loopback  
             inet addr:127.0.0.1  Mask:255.0.0.0
             UP LOOPBACK RUNNING  MTU:16436  Metric:1
             RX packets:52012956 errors:0 dropped:0 overruns:0 frame:0
             TX packets:52012956 errors:0 dropped:0 overruns:0 carrier:0
             collisions:0 txqueuelen:0 
             RX bytes:905082901 (863.1 MB)  TX bytes:905082901 (863.1 MB)
   

2. As the root user, verify the network configuration by using the ping command to test the connection from each node in your cluster to all the other nodes. For example, as the root user, you might run the following commands on each node:

   # ping -c 3 racnode1.example.com
   # ping -c 3 racnode1
    
   # ping -c 3 racnode2.example.com
   # ping -c 3 racnode2
   

   You should not get a response from the nodes using the ping command for the virtual IPs (racnode1-vip, racnode2-vip) or the SCAN IPs until after Oracle Clusterware is installed and running. If the ping commands for the public addresses fail, resolve the issue before you proceed.

3. Ensure that you can access the default gateway with a ping command. To identify the default gateway, use the route command, as described in the Oracle Enterprise Linux Help utility.

About Setting the Time on Both Nodes

Before starting the installation, ensure that the date and time settings on both nodes are set as closely as possible to the same date and time. A cluster time synchronization mechanism ensures that the internal clocks of all the cluster members are synchronized. For Oracle RAC on Linux, you can use either the Network Time Protocol (NTP) or the Oracle Cluster Time Synchronization Service.

NTP is a protocol designed to synchronize the clocks of servers connected by a network. When using NTP, each server on the network runs client software to periodically make timing requests to one or more servers, referred to as reference NTP servers. The information returned by the timing request is used to adjust the server's clock. All the nodes in your cluster should use the same reference NTP server.

If you do not configure NTP, Oracle will configure and use the Cluster Time Synchronization Service (CTSS). CTSS can also be used to synchronize the internal clocks of all the members in the cluster. CTSS keeps the member nodes of the cluster synchronized. CTSS designates the first node in the cluster as the master and then synchronizes all other nodes in the cluster to have the same time as the master node. CTSS does not use any external clock for synchronization.

About Configuring Kernel Parameters

OUI checks the current settings for various kernel parameters to ensure they meet the minimum requirements for deploying Oracle RAC. For production database systems, Oracle recommends that you tune the settings to optimize the performance of your particular system.

About Performing Platform-Specific Configuration Tasks

You may be required to perform special configuration steps that are specific to the operating system on which you are installing Oracle RAC, or for the components used with your cluster. The following list provides examples of operating-specific installation tasks:

• Configure the use of Huge Pages on SUSE Linux, Red Hat Enterprise Linux, or Oracle Enterprise Linux.

• Configure the hangcheck-timer module on SUSE Linux, Red Hat Enterprise Linux, or Oracle Enterprise Linux.

• Set shell limits for the oracle user on Red Hat Linux or Oracle Enterprise Linux systems to increase the number of files and processes available to Oracle Clusterware and Oracle RAC.

• Start the Telnet service on Microsoft Windows.

• Create X library symbolic links on HP-UX.

• Configure network tuning parameters on AIX Based Systems.

Locating the Oracle Inventory Directory

The Oracle Inventory (oraInventory) directory is the central inventory record of all Oracle software installations on a server. The oraInventory directory contains the following:

• A registry of the Oracle home directories (Oracle grid infrastructure and Oracle Database) on the system

• Installation logs and trace files from installations of Oracle software. These files are also copied to the respective Oracle homes for future reference

The oraInventory directory is created by OUI during installation.By default, the Oracle Inventory directory is not installed under the Oracle Base directory. This is because all Oracle software installations share a common Oracle Inventory, so there is only one Oracle Inventory for all users, whereas each user that performs a software installation can use a separate Oracle base directory.

If you have an existing Oracle Inventory, then ensure that you use the same Oracle Inventory for all Oracle software installations, and ensure that all Oracle software users you intend to use for installation have permissions to write to this directory.

To determine if you have an Oracle central inventory directory (oraInventory) on your system:

1. Run the following command to check for an existing Oracle Inventory directory:

   # more /etc/oraInst.loc
   

2. If the oraInst.loc file exists, then the output from this command is similar to the following:

   inventory_loc=/u01/app/oraInventory
   inst_group=oinstall
   

   In the previous output example:

   • The inventory_loc group shows the location of the Oracle Inventory.

   • The inst_group parameter shows the name of the Oracle Inventory group (in this example, oinstall).

3. If the Oracle Inventory directory does not exist, the command returns an error message indicating that the file or directory does not exist.

   If the Oracle Inventory directory does not exist, you do not need to create one prior to installing the Oracle software.

Creating the Oracle Grid Infrastructure Home Directory

During installation, you are prompted to provide a path to a home directory to store Oracle grid infrastructure binaries. OUI installs Oracle Clusterware and Oracle ASM into a directory referred to as Grid_home. Ensure that the directory path you provide meets the following requirements:

• It should be created in a path outside existing Oracle homes.

• It should not be located in a user home directory.

• It should be created either as a subdirectory in a path where all files can be owned by root, or in a unique path.

• If you create the path before installation, then it should be owned by the installation owner of Oracle grid infrastructure (oracle or grid), and set to 775 permissions.

Before you start the installation, you must have sufficient disk space on a file system for the Oracle grid infrastructure directory. The file system that you use for the Grid home directory must have at least 4.5 GB of available disk space.

The path to the Grid home directory must be the same on all nodes. As the root user, you should create a path compliant with Oracle Optimal Flexible Architecture (OFA) guidelines, so that OUI can select that directory during installation.

To create the Grid home directory:

To create the Grid home directory as the root user, enter the following commands:

# mkdir -p /u01/grid
# chown -R oracle:oinstall /u01/grid

Creating the Oracle Base Directory

Oracle Universal Installer (OUI) creates the Oracle base directory for you in the location you specify. This directory is owned by the user performing the installation. The Oracle base directory (ORACLE_BASE) helps to facilitate the organization of Oracle installations, and helps to ensure that installations of multiple databases maintain an Optimal Flexible Architecture (OFA) configuration. OFA guidelines recommend that you use a path similar to the following for the Oracle base directory:

/mount_point/app/user

In the preceding path example, the variable mount_point is the mount point directory for the file system where you intend to install the Oracle software and user is the Oracle software owner (typically oracle). For OUI to recognize the path as an Oracle software path, it must be in the form u0[1-9]/app, for example, /u01/app.

The path to the Oracle base directory must be the same on all nodes. The permissions on the Oracle base directory should be at least 750.

About the Oracle Home Directory

The Oracle home directory is the location in which the Oracle RAC software is installed. You can use a Oracle home directory created in the local file system, for example, /u01/app/oracle/product/11.2.0/dbhome_1. The same directory must exist on every node in the cluster. You do not need to create these directories prior to installation. By default, the installer will suggest a subdirectory of the Oracle base directory for the Oracle home.

You can also use a shared Oracle home. The location of the shared Oracle home can be on network storage, or a supported cluster file system such as Oracle Automatic Storage Management Cluster File System (Oracle ACFS). For more information about Oracle ACFS, see Oracle Database Storage Administrator's Guide.

If you use the local file system for the Oracle home directory, and you want to install a different versions of Oracle RAC or Oracle Database on the same server, then you must use a separate Oracle home directory for each software installation. Multiple versions of the same product or different products can run from different Oracle homes concurrently. Products installed in one Oracle home do not conflict or interact with products installed in another Oracle home.

Using different Oracle homes for your installed software allows you to perform maintenance operations on the Oracle software in one home without effecting the software in another Oracle home. However, it also increases your software maintenance costs, because each Oracle home must be upgraded or patched separately.

About Shared Storage

Each node in a cluster requires external shared disks for storing the Oracle Clusterware (Oracle Cluster Registry and voting disk) files, and Oracle Database files. The supported types of shared storage depend upon the platform you are using, for example:

• Automatic Storage Management (strongly recommended)

• A supported cluster file system, such as OCFS2 for Linux, OCFS for Microsoft Windows, or General Parallel File System (GPFS) on IBM platforms

• Network file system (NFS), which is not supported on AIX Based Systems, Linux on POWER, or on IBM zSeries Based Linux

• (Upgrades only) Shared disk partitions consisting of block devices or raw devices. Block devices are disk partitions that are not mounted using the Linux file system. Oracle Clusterware and Oracle RAC write to these partitions directly.

  Note:

  You cannot use OUI to install Oracle Clusterware files on block or raw devices. You cannot put Oracle Clusterware binaries and files on Oracle Automatic Storage Management Cluster File System (Oracle ACFS).

For all installations, you must choose the storage option that you want to use for Oracle Clusterware files and Oracle Database files.

If you decide to use OCFS2 to store the Oracle Clusterware files, you must use the proper version of OCFS2 for your operating system version. OCFS2 works with Oracle Enterprise Linux and Red Hat Linux kernel version 2.6

The examples in this guide use Oracle ASM to store the Oracle Clusterware and Oracle Database files. The Oracle grid infrastructure and Oracle RAC software will be installed on disks local to each node, not on a shared file system.

Configuring Files on an NAS Device for Use with Oracle ASM

To use an NFS file system, it must be on a certified NAS device. If you have a certified network attached storage (NAS) device, then you can create zero-padded files in an NFS mounted directory and use those files as disk devices in an Oracle ASM disk group.

To ensure high availability of Oracle Clusterware files on Oracle ASM, you need to have at least 2 GB of disk space for Oracle Clusterware files in three separate failure groups, with at least three physical disks. Each disk must have at least 1 GB of capacity to ensure that there is sufficient space to create Oracle Clusterware files.

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.

• A disk group should not contain more than one partition on a single physical disk device.

• Using logical volumes as a device in an Automatic Storage Management disk group is not supported with Oracle RAC.

• The user account with which you perform the installation (oracle) must have write permissions to create the files in the path that you specify.

To configure NAS device files for creating disk groups:

1. Add and configure access to the disks to the NAS device. Make sure each cluster node has been granted access to all the disks that will be used by Oracle grid infrastructure software and Oracle Database software.

   Refer to your NAS device documentation for more information about completing this step.

2. On a cluster node, log in as the root user (or use sudo for the following steps).

3. Configure access to the disks on the NAS devices. The process for completing this step can vary depending on the type of disks and the type of NAS service.

   One example of the configuration process is shown here. The first step is to create a mount point directory on the local system:

   # mkdir -p /mnt/oracleasm
   

4. To ensure that the NFS file system is mounted when the system restarts, add an entry for the file system in the mount file /etc/fstab.

   For more information about editing the mount file for the operating system, refer to the Linux man pages. For more information about recommended mount options, refer to Oracle Grid Infrastructure Installation Guide for Linux.

5. Enter a command similar to the following to mount the NFS file system on the local system, where host is the hostname or IP address of the file server, and pathname is the location of the storage within NFS (for example, /public):

   # mount <host>:<pathname> /mnt/oracleasm
   

6. Choose a name for the disk group that you want to create, for example, nfsdg.

7. Create a directory for the files on the NFS file system, using the disk group name as the directory name, for example:

   # mkdir /mnt/oracleasm/nfsdg
   

8. Use commands similar to the following to create the required number of zero-padded files in this directory:

   # dd if=/dev/zero of=/mnt/oracleasm/nfsdg/disk1 bs=1024k count=1000
   

   This example creates a 1 GB file named disk1 on the NFS file system. You must create one, two, or three files respectively to create an external, normal, or high redundancy disk group.

9. Enter the following commands to change the owner, group, and permissions on the directory and files that you created:

   # chown -R oracle:dba /mnt/oracleasm
   # chmod -R 660 /mnt/oracleasm
   

10. When installing Oracle RAC, if you choose to create an Oracle ASM disk group, you will need to change the disk discovery path to specify a regular expression that matches the file names you created, for example, /mnt/oracleasm/nfsdg/*.

Using ASMLib to Mark the Shared Disks as Candidate Disks

When you reboot the server, unless you have configured special files for device persistence, a disk that appeared as /dev/sdg before the system shutdown can appear as /dev/sdh after the system is restarted. If you use ASMLib to configure the disks, then when you reboot the node:

• The disk device names do not change

• The ownership and group membership for these disk devices remains the same

• You can copy the disk configuration implemented by ASM to other nodes in the cluster by running a simple command

The following sections describe how to configure and use ASMLib for your shared disk devices:

• Installing ASMLib

• Configuring ASMLib

• Using ASMLib to Create ASM Disks

Configuring Disk Device Persistence

By default, the Linux 2.6 kernel device file naming scheme udev dynamically creates device file names when the server is started, and assigns ownership of them to root. If udev applies default settings, then it changes device file names and owners for voting disks or Oracle Cluster Registry partitions, corrupting them when the server is restarted. For example, a voting disk on a device named /dev/sdd owned by the user grid may be on a device named /dev/sdf owned by root after restarting the server.

If you use ASMLIB, then you do not need to ensure permissions and device path persistency in udev. If you do not use ASMLib, then you must create a custom rules file. When udev is started, it sequentially carries out rules (configuration directives) defined in rules files. These files are in the path /etc/udev/rules.d/. Rules files are read in lexical order. For example, rules in the file 10-wacom.rules are parsed and carried out before rules in the rules file 90-ib.rules.

Where rules files describe the same devices, on Asianux, Red Hat, and Oracle Enterprise Linux, the last file read is the one that is applied. On SUSE 2.6 kernels, the first file read is the one that is applied.

To configure a rules file for disk devices, refer to Chapter 3 in Oracle Grid Infrastructure Installation Guide for Linux.