Mirror pve-root Using LVM RAID1

What this means:

You configure a mirror (RAID1) so that any write to pve-root is also written to sda1. If your NVMe dies, you can still boot from sda1.

🧱 Requirements:

• sda1 must be equal to or larger than pve-root (96 GB in your case)
• You must convert pve-root into a RAID1 logical volume (LVM mirror)
• Some downtime or maintenance mode required

🧰 How-To (Overview Only):

• Backup First! (Always)
• Check current setup:
  • lvdisplay pve/root
• Wipe and prep sda1:
  • pvcreate /dev/sda
  • vgextend pve /dev/sda
• Convert pve-root to RAID1:
  • lvconvert --type mirror -m1 --mirrorlog core pve/root /dev/sda

This mirrors pve/root from your NVMe disk onto sda.

• Confirm with:
  • lvs -a -o +devices

root@pve:~# lvs -a -o +devices
  LV              VG  Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert Devices
  data            pve twi-aotz-- 794.30g             0.01   0.24                             data_tdata(0)
  [data_tdata]    pve Twi-ao---- 794.30g                                                     /dev/nvme0n1p3(26624)
  [data_tmeta]    pve ewi-ao----   8.10g                                                     /dev/nvme0n1p3(229966)
  [lvol0_pmspare] pve ewi-------   8.10g                                                     /dev/nvme0n1p3(232040)
  root            pve mwi-aom---  96.00g                                    100.00           root_mimage_0(0),root_mimage_1(0)
  [root_mimage_0] pve iwi-aom---  96.00g                                                     /dev/nvme0n1p3(2048)
  [root_mimage_1] pve iwi-aom---  96.00g                                                     /dev/sda(0)
  swap            pve -wi-ao----   8.00g                                                     /dev/nvme0n1p3(0)

• Optional but smart: Update your bootloader (grub) to know how to boot from either disk:
  • update-initramfs -u
  • update-grub
  • grub-install /dev/sda

✅ Pros:

• Real-time mirroring (RAID1)
• Transparent failover if one device fails (bootable if configured)

⚠️ Cons:

• Adds complexity
• If misconfigured, can break boot
• Doesn’t protect against file deletion or config mistakes (RAID is not a backup)

how to check the mirror status, detect failures, and know when to do maintenance:

Use lvdisplay for more detail:

lvdisplay /dev/pve/root

Look for:

• Mirror status: OK (or similar)
• If a device has failed, you’ll see something like “failed” or “inconsistent”