Using mdadm to Manage RAID and Multipath Storage on Linux: A Practical Guide with Examples

The mdadm command is a powerful tool for managing multiple device sets on Linux systems. It plays a crucial role in creating and maintaining RAID arrays, which provide redundancy and performance benefits, and multipath setups, which ensure data availability in case of hardware failure. Let's delve into how you can use mdadm to harness these powerful storage features, complete with practical examples.

Creating RAID Devices with mdadm

1. Define Your Configuration:

The /etc/mdadm.conf file is where you specify the devices and RAID level for your array.

Example: RAID 1 (Mirroring)

DEVICE /dev/sd[b,c]1  
ARRAY /dev/md0 level=raid1 raid-devices=2 /dev/sdb1 /dev/sdc1

This configuration creates a RAID 1 array (/dev/md0) that mirrors data across two devices (/dev/sdb1 and /dev/sdc1).

Example: RAID 5 (Striping with Parity)

DEVICE /dev/sd[b-d]1
ARRAY /dev/md0 level=raid5 raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1

This configuration creates a RAID 5 array (/dev/md0) that stripes data across three devices with parity information for fault tolerance.

2. Create the RAID Array:

Use mdadm with the -C (create) option and the details from your configuration:

# RAID 1 example
sudo mdadm -C /dev/md0 --level=raid1 --raid-devices=2 /dev/sdb1 /dev/sdc1

# RAID 5 example
sudo mdadm -C /dev/md0 --level=raid5 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1

3. Verify RAID Status:

Check the status of your newly created RAID array:

sudo mdadm --detail /dev/md0

You should see information about the RAID level, state (active, syncing, etc.), device status, and more.

Creating Multipath Devices with mdadm

Multipathing provides an additional layer of reliability by creating multiple paths to access a storage device.

sudo mdadm -C /dev/md1 --level=multipath --raid-devices=2 /dev/mapper/mpatha /dev/mapper/mpathb

This command creates a multipath device (/dev/md1) using two paths (/dev/mapper/mpatha and /dev/mapper/mpathb) that likely correspond to different physical disks.

Key Considerations

• Choose the Right RAID Level:
  • RAID 0: Best for performance but no redundancy.
  • RAID 1: Offers redundancy with mirroring.
  • RAID 5: Good balance of performance and redundancy.
  • RAID 6: More redundancy than RAID 5 but slightly slower.
  • RAID 10: Combines mirroring and striping for both performance and redundancy.
• Data Backup: RAID is not a backup solution; always maintain regular backups.
• Hardware Compatibility: Ensure your hardware (controllers, disks) supports your chosen RAID level.

Conclusion

mdadm empowers you to create robust and fault-tolerant storage solutions on Linux. By mastering its capabilities, you can optimize your server's performance and protect your valuable data.

Let me know if you'd like more in-depth examples or have any specific scenarios you'd like to explore!

Google Apps Wizard cPanel plugin

This tool was developed for web hosting companies, webmasters and website developers that have to setup domains with Google Apps in the everyday work. The purpose of Google Apps Wizard cPanel plugin is to facilitate the steps needed to work with Google Apps services. cPanel end user doesn’t need to have any prior knowledge of DNS records management while working with this tool.

http://code.google.com/p/google-apps-wizard-cpanel-plugin/

Installation

Run the following shell commands as root via SSH:

# wget http://google-apps-wizard-cpanel-plugin.googlecode.com/files/gaw-2.0.tar
# tar -xf gaw-2.0.tar
# cd gaw-2.0
# ./gawinstall.sh
# cd ..
# rm -Rfv gaw-2.0/ gaw-2.0.tar

Go to WHM >> Main >> Plugins >> Google Apps Wizard and click Update Now.
Upgrade

If you running version 2+ please skip this part.

# wget http://google-apps-wizard-cpanel-plugin.googlecode.com/files/gaw-2.0.tar
# tar -xf gaw-2.0.tar
# cd gaw-2.0
# ./gawupdate.sh
# cd ..
# rm -Rfv gaw-2.0/ gaw-2.0.tar

Uninstall

# wget http://google-apps-wizard-cpanel-plugin.googlecode.com/files/gaw-2.0.tar
# tar -xf gaw-2.0.tar
# cd gaw-2.0
# ./gawuninstall.sh
# cd ..
# rm -Rfv gaw-2.0/ gaw-2.0.tar

Multi-languages support

The language files folder is located at: /usr/local/cpanel/base/3rdparty/GoogleAppsWizard/lang/
The en.php is the default fallback language file so do not delete it!
To create new language files you must use an existing cPanel prefix.
You can see your available languages by navigating to: Main >> Locales >> View Available Locales.

Templates support

The Google Apps Wizard plugin support third party cPanel templates.
All you need to do is to copy the default template to your third party template folder.
Template path: /usr/local/cpanel/base/frontend/x3/gaw
Example command: # cp /usr/local/cpanel/base/frontend/x3/gaw /usr/local/cpanel/base/frontend/{Your custom template folder name}/

Mastering Installatron: A Guide to Installing and Uninstalling on Linux Servers

Installatron is a powerful web application installer that simplifies the deployment of popular scripts and CMS platforms like WordPress, Joomla, Drupal, and many more. It's a valuable tool for web hosting providers and system administrators who want to automate the process of setting up websites and applications for their clients.

In this guide, we'll walk you through the steps for installing and uninstalling Installatron on your Linux or FreeBSD server.

Installing Installatron

1. Download the Installer Script: Open your terminal and run the following command to download the Installatron installation script:

wget http://data.installatron.com/installatron-plugin.sh

2. Make the Script Executable: Give the script execute permissions:

chmod +x installatron-plugin.sh

3. Run the Installer: Execute the script to begin the installation process:

./installatron-plugin.sh -f

The -f flag indicates a forced installation, which might be necessary in some cases.

The script will automatically install Installatron and its dependencies.

Uninstalling Installatron

If you need to remove Installatron from your server, follow these steps:

1. Remove the Core Components: Execute the following commands to remove the core Installatron files:

rpm -e installatron-server
rm -fr /usr/local/installatron
rm -f /etc/cron.d/installatron

2. Delete User Install Data (Optional): If you want to completely remove all traces of Installatron and the applications it installed, you can delete the user install data. Exercise caution here, as this will delete all data associated with installed applications.

rm -fr /var/installatron

Important Considerations:

• Backups: Before installing or uninstalling any software, including Installatron, it's always a good practice to back up your server's data. This ensures you can easily restore your system in case anything goes wrong.
• Dependencies: Installatron may rely on certain dependencies (like PHP or MySQL). Make sure these dependencies are installed and configured correctly before installing Installatron.
• User Data: If you decide to remove user install data, be absolutely sure you don't need any of the installed applications or their data.

By following these instructions, you can confidently install and uninstall Installatron on your Linux server, giving you a versatile tool for managing web applications efficiently.