Managing Multipath Disks with Oracle ASM: A Comprehensive Guide

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Introduction

Oracle Automatic Storage Management (ASM) is a powerful and efficient solution for managing disk storage in Oracle databases. It simplifies storage administration by abstracting away the complexities of managing physical disks. When it comes to large-scale databases, performance, scalability, and high availability are critical factors. To meet these requirements, Oracle ASM can be integrated with Multipath Disks, providing redundancy and load balancing capabilities. In this article, we’ll explore the concepts of Oracle ASM and Multipath Disks, along with practical coding examples to demonstrate their usage.

What is Oracle ASM?

Oracle ASM is a specialized volume manager and file system designed to simplify the storage of Oracle database files. It was first introduced in Oracle 10g and has since become the default choice for Oracle database storage management. Oracle ASM abstracts the physical disk layout and manages the disk I/O efficiently, enhancing database performance and availability.

Some key features of Oracle ASM include:

  1. Automatic Load Balancing: Oracle ASM automatically distributes data across available disks to balance I/O and maximize performance.
  2. Mirroring and Redundancy: It provides various options for redundancy, such as normal and high redundancy, ensuring data availability in case of disk failures.
  3. Scalability: Oracle ASM supports the addition of disks and storage online, enabling databases to scale without downtime.
  4. Striping: Data is striped across disks, improving I/O performance.

Multipath Disks: An Overview

Multipath disks are a solution for ensuring high availability and load balancing in storage systems. They are particularly useful in environments where system administrators need to account for disk failures and provide continuous access to data. Multipath I/O (MPIO) enables the use of multiple paths to the same storage device, ensuring redundancy and fault tolerance.

Key benefits of Multipath Disks include:

  1. Redundancy: In the event of a hardware failure or path disruption, data access can continue through an alternate path.
  2. Load Balancing: Multipath I/O distributes I/O requests across multiple paths, enhancing performance.
  3. Failover: The system can automatically switch to an available path in the event of path failure.
  4. Improved Availability: Multipath disks contribute to high availability configurations by eliminating single points of failure.

Integrating Oracle ASM with Multipath Disks

Integrating Oracle ASM with Multipath Disks is a strategic move for enhancing database availability and performance. The following steps outline the process:

1. Configure Multipath Disks

Before integrating Oracle ASM with Multipath Disks, you need to set up the Multipath software on your system. On Linux, this typically involves configuring the Device Mapper Multipath (DM-Multipath) service. You can use tools like multipath and multipathd to manage and monitor multipath devices.

Here is an example of configuring Multipath on a Linux system:

bash
# Install the multipath tools
sudo apt-get install multipath-tools# Configure multipath
sudo vi /etc/multipath.conf# Add configuration for your storage devices
# For example:
# devices {
# device {
# vendor “VENDOR”
# product “PRODUCT”
# }
# }

# Reload the multipath configuration
sudo multipath -v2

2. Create Multipath Devices

After configuring Multipath, you can create Multipath devices for your storage. These devices will be used by Oracle ASM for database storage.

bash
# Discover Multipath devices
sudo multipath -ll# Create a Multipath device for Oracle ASM
sudo oracleasm createdisk ASM_DISK1 /dev/mapper/MULTIPATH_DEVICE1
sudo oracleasm createdisk ASM_DISK2 /dev/mapper/MULTIPATH_DEVICE2

3. Configure Oracle ASM

Once the Multipath devices are created, you can configure Oracle ASM to use them for database storage. This involves creating ASM disk groups and specifying the Multipath devices as candidate disks.

sql
-- Connect to SQL*Plus as the SYS user
sqlplus / as sysdba— Create a new ASM disk group
CREATE DISKGROUP DATA_GROUP
NORMAL REDUNDANCY
DISK ‘ORCL:ASM_DISK1’, ‘ORCL:ASM_DISK2’;— List the ASM disk groups
SELECT name, state FROM v$asm_diskgroup;

4. Use Multipath Disks in Oracle ASM

With the Multipath devices configured and Oracle ASM set up, you can start using the Multipath disks for database storage.

sql
-- Create a tablespace on the ASM disk group
CREATE TABLESPACE my_tablespace
DATAFILE '+DATA_GROUP' SIZE 100M;— Create a table in the new tablespace
CREATE TABLE my_table (
id NUMBER,
name VARCHAR2(50)
);

Benefits of Oracle ASM with Multipath Disks

The integration of Oracle ASM with Multipath Disks offers several benefits to Oracle database administrators:

  1. High Availability: Multipath Disks ensure continuous access to data, even in the face of hardware failures or path disruptions. This contributes to high availability configurations.
  2. Performance: Load balancing and striping of data across Multipath devices can significantly improve I/O performance, especially in I/O-intensive database workloads.
  3. Simplified Management: Oracle ASM abstracts the physical storage layout and simplifies the management of storage. Administrators don’t need to worry about the underlying disk configuration.
  4. Scalability: Oracle ASM allows for online addition of disks, making it easy to scale the storage as database requirements grow.
  5. Redundancy: Oracle ASM provides options for redundancy, ensuring data integrity and availability. Multipath Disks add an extra layer of redundancy, making it a robust solution.

Conclusion

In this article, we explored the integration of Oracle ASM with Multipath Disks, providing a comprehensive guide to configuring and using these technologies together. By configuring Multipath Disks and connecting them to Oracle ASM, you can significantly enhance the availability and performance of your Oracle databases.

When working with Oracle ASM and Multipath Disks, it’s essential to follow best practices, keep your storage software and drivers up to date, and regularly monitor the health and performance of your storage environment. This combination is particularly valuable for large-scale and mission-critical database systems where high availability and performance are non-negotiable.

Remember, the exact steps and configurations may vary depending on your specific environment, hardware, and Oracle ASM version, so always refer to official documentation and seek expert advice when implementing these solutions in a production environment.