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LWM-Linux/08 - Advanced Linux Administration/RAID and LVM.md

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RAID and LVM

1. RAID (Redundant Array of Independent Disks)

RAID is a technology that combines multiple disk drive components into a logical unit for data redundancy and performance improvement.

Types of RAID:

a) RAID 0 (Striping):

  • Data is split across multiple disks
  • Improves performance but no redundancy
  • Minimum 2 disks required

b) RAID 1 (Mirroring):

  • Data is duplicated on two or more disks
  • Provides redundancy but no performance improvement for writes
  • Minimum 2 disks required

c) RAID 5 (Striping with parity):

  • Data and parity information are striped across all disks
  • Good balance of performance and redundancy
  • Can survive one disk failure
  • Minimum 3 disks required

d) RAID 6 (Striping with double parity):

  • Similar to RAID 5 but with two parity blocks
  • Can survive two disk failures
  • Minimum 4 disks required

e) RAID 10 (Stripe of mirrors):

  • Combines RAID 1 and RAID 0
  • Provides both redundancy and performance improvement
  • Minimum 4 disks required

Setting up RAID in Linux:

1. Install mdadm:

sudo apt-get install mdadm

2. Create a RAID array (example for RAID 5):

sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd

3. Create a filesystem on the RAID array:

sudo mkfs.ext4 /dev/md0

4. Mount the RAID array:

sudo mount /dev/md0 /mnt/raid

5. Save the RAID configuration:

sudo mdadm --detail --scan >> /etc/mdadm/mdadm.conf

2. LVM (Logical Volume Management)

LVM is a device mapper framework that provides logical volume management for the Linux kernel. It allows for more flexible disk space management.

Key concepts:

  • a) Physical Volume (PV): Physical disks or partitions
  • b) Volume Group (VG): Group of physical volumes
  • c) Logical Volume (LV): Virtual partitions created from a volume group

Setting up LVM:

1. Install LVM:

sudo apt-get install lvm2

2. Create Physical Volumes:

sudo pvcreate /dev/sdb /dev/sdc

3. Create a Volume Group:

sudo vgcreate myvg /dev/sdb /dev/sdc

4. Create Logical Volumes:

sudo lvcreate -n mylv1 -L 50G myvg
sudo lvcreate -n mylv2 -l 100%FREE myvg

5. Create filesystems on Logical Volumes:

sudo mkfs.ext4 /dev/myvg/mylv1
sudo mkfs.ext4 /dev/myvg/mylv2

6. Mount Logical Volumes:

sudo mount /dev/myvg/mylv1 /mnt/lv1
sudo mount /dev/myvg/mylv2 /mnt/lv2

Advantages of LVM:

    1. Flexible capacity management
    1. Easy resizing of logical volumes
    1. Snapshots for backup purposes
    1. Striping and mirroring capabilities

Combining RAID and LVM:

You can use RAID as the underlying storage for LVM, providing both redundancy and flexibility:

    1. Create a RAID array
    1. Use the RAID array as a Physical Volume for LVM
    1. Create Volume Groups and Logical Volumes on top of the RAID array

Example:

sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
sudo pvcreate /dev/md0
sudo vgcreate myvg /dev/md0
sudo lvcreate -n mylv1 -L 100G myvg
sudo mkfs.ext4 /dev/myvg/mylv1
sudo mount /dev/myvg/mylv1 /mnt/data

This setup provides the redundancy of RAID 5 with the flexibility of LVM.

Maintenance and Monitoring:

1. RAID:

  • Check RAID status: cat /proc/mdstat
  • Detailed RAID info: sudo mdadm --detail /dev/md0

2. LVM:

  • Display PV info: sudo pvdisplay
  • Display VG info: sudo vgdisplay
  • Display LV info: sudo lvdisplay

Remember, LVM provides flexibility, scalability, and ease of maintenance, while RAID enhances performance and data protection! 😊🚀

Source: Conversation with Copilot, 7/12/2024