Setup Software RAID-1 on Ubuntu 20.04

紀錄一下如何在 Linux 上架 RAID-1.

Create RAID-1 for Non-root Directory

假設電腦有三顆 SSD,

/dev/nvme0n1: 256 GB, 已安裝 Ubuntu 20.04, /dev/nvme0n1p2 掛載在 /
/dev/nvme1n1: 1 TB, 準備做 RAID-1, 掛在 /data
/dev/nvme2n1: 1 TB, 準備做 RAID-1, 掛在 /data

Required Packages

Install mdadm (Multiple Devices Admin)
```
$ sudo apt install mdadm
```

Disk Status Check

List block devices
```
$ sudo lsblk
```

Display the partition table

$ sudo parted -a optimal /dev/nvme1n1 print

Disk Cleanup

Change to root
```
$ sudo -i
```

Wipe entire disk:

$ dd if=/dev/nvme1n1 of=/dev/sdX bs=1M
$ dd if=/dev/nvme2n1 of=/dev/sdX bs=1M

Or, Wipe sidk using wipefs:

$ umount /dev/nvme1n1p?; wipefs --all --force /dev/nvme1n1p?; wipefs --all --force /dev/nvme1n1
$ umount /dev/nvme2n1p?; wipefs --all --force /dev/nvme2n1p?; wipefs --all --force /dev/nvme2n1

Disk Partition

Create GUID partition table (GPT)
```
$ gdisk /dev/nvme1n1
$ gdisk /dev/nvme2n1
```
- Enter o for new empty GUID partition table (GPT)
- Enter y to confirm your decision
- Enter n for new partition
- Enter for default of first partition
- Enter for default of the first sector
- Enter for default of the last sector
- Enter fd00 for Linux RAID type
- Enter w to write changes
- Enter y to confirm your decision

Examine disk status and should report (type ee)

$ mdadm --examine /dev/nvme1n1 /dev/nvme2n1

Examine the first partition of the disk and should report No md superblock detected
```
$ mdadm --examine /dev/nvme1n1p1 /dev/nvme2n1p1
```

RAID-1 Creation

Create the RAID-1 array

$ mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/nvme1n1p1 /dev/nvme2n1p1 

Check the array is created and synced

$ cat /proc/mdstat
$ mdadm --detail /dev/md0

Filesystem Creation

Format /dev/md0 as ext4

$ mkfs.ext4 -m 0 -E lazy_itable_init=0,lazy_journal_init=0 /dev/md0

Check disk status

$ sudo parted -a optimal /dev/md0 print

Update mdadm config

$ /usr/share/mdadm/mkconf | tee /etc/mdadm/mdadm.conf

Disk Mount

Mount disk temporarily

$ mkdir -p /data
$ mount /dev/md0 /data

Get disk’s UUID
```
$ blkid /dev/md0
```

Edit /etc/fstab and add an entry for file system information

UUID=<the UUID you have in the clipboard>    /data    ext4    defaults    0 2

Update initramfs and reboot
```
$ update-initramfs -u -k all
$ reboot
```

Create RAID-1 for Root Directory

需要使用 Ubuntu server image 安裝, 可參考 Looking to create a Software RAID 1 setup for your 2-disk server on Ubuntu Server 20.04?

Intel Rapid Storage Technology

Intel Rapid Storage Technology (RST) 是一種 firmware RAID, 依照 Ubuntu 官方的說法, Linux 可能可以用 Intel RST, 也可能不行 (WTX …). 最好的方法是把 Intel RST 關閉.

這一篇 Reddit 的文章有說 Intel 有 submit RST 相關的 code 到 Linux kernel, 但被拒絕了. 所以至今, Intel RST 基本上是無法完全 Support 的. 所以還是改用 Software RAID 吧.

Reference

Linux Written on November 3rd , 2021 by Borting

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