Skip to main content

LVM + dm-cache (unencrypted)

NOTE: This partition scheme is tailored towards a desktop computer setup with enough RAM and no SWAP (and therefore no hibernate/suspend-to-disk support).

CAUTION: This setup does NOT utilize LUKS disk encryption.

LVM cache combines the benefits of a fast mass storage device (e.g. SSD) with a slow mass storage device (HDD), utilizing the former as a read/write cache for the latter. This allows the system to manage blocks of data in a way such that often used blocks are kept on the fast cache device, making the whole system a lot more responsive. Over time the cache device fills up with frequently accessed data and the system accesses the cache device more often than the origin device (the HDD). This can be used to cost-effectively speed up an inexpensive large storage device (think Apple Fusion Drive).

This guide assumes the following:

  • /dev/nvme0n1 is the primary disk (cache device)
  • /dev/sda is the secondary disk (origin device)

Nomenclature

On-disk Logical
ExpressionTerm AbbreviationMeaningDescription
Physical Volume (PV) PV Unixpartitioning blockformat deviceto node,be usablecombined forin a VG to a common storage by LVM. Examples: a hard disk, an MBR or GPT partition.pool
Volume Group (VG) VGGroupGrouping of one or more PVs thatto serves asprovide a containercombined forstorage LVs. PEs are allocatedpool from awhich VGstorage forcan abe LV.requested in the form of LVs.
Logical Volume (LV) LV "Virtual/logicalpartition partition"format that resides in a VG and is composed of PEs. LVs are Unix block devices analogous to physical partitions, e.g. theywhich can be directlyaccessed formatted withlike a fileblock system.
Physical ExtentsPEThe smallest contiguous extent (default 4 MiB) in the PV that can be assigneddevice to ahold LV.file Thinksystems ofand PEs as parts of PVs that can be allocated to any LV.data.

Preparing the cache device

  1. List available disks

    fdisk -l

  2. Start partitionaing tool for primary disk (cfdisk is a little easier to use as it has a nice TUI)

    WARNING: Make sure to select your actually desired device!

    cfdisk /dev/nvme0n1

  3. Partition with the following scheme

    FS Type Size Mount Point Comment

    | vfat | 1G | /boot | EFI System | | LVM | (remaining) | | Linux LVM |

Preparing the origin device

  1. Start partioning tool for secondary disk

    WARNING: Make sure to select your actually desired device!

    cfdisk /dev/sda

  2. Partition with the following scheme

    FS Type Size Mount Point Comment

    | LVM | (all) | | Linux LVM |

Creating physical volumes, volume group and logical volumes

  1. Create LVM physical volumes

    pvcreate /dev/nvme0n1p2   # SSD
pvcreate /dev/sda1        # HDD

  2. Create LVM volume group

    NOTE: vg0 is used as an example here. Use whatever you like.

    vgcreate vg0 /dev/nvme0n1p2 /dev/sda1

  3. Create LVM logical volumes

    lvcreate -l 100%FREE -n lv_root vg0 /dev/sda1
lvcreate --type cache-pool -n lv_cache -l 100%FREE vg0 /dev/nvme0n1p2

# Link cache devices
lvconvert --type cache --cachepool vg0/lv_cache vg0/lv_root

Formatting devices

  1. Create partitions 
    mkfs.fat -F 32 /dev/nvme0n1p1        # EFI System Partition
mkfs.btrfs /dev/mapper/vg0-lv_root   # Btrfs root file system
  2. Create Btrfs subvolumes 
    # First, mount root file system
mount /dev/mapper/vg0-lv_root /mnt

# Create subvolumes
btrfs subvolume create /mnt/@
btrfs subvolume create /mnt/@home
  3. Mount partitions 
    # Unmount the root file system
umount -R /mnt

# Mount the @ subvolume
mount /dev/mapper/vg0-lv_root -o noatime,compress-force=zstd,space_cache=v2,subvol=@ /mnt

# Create mountpoints
mkdir -p /mnt/{boot,home}

# Mount the remaining partitions/subvolumes
mount /dev/nvme0n1p1 /mnt/boot
mount /dev/mapper/vg0-lv_root -o noatime,compress-force=zstd,space_cache=v2,subvol=@home /mnt/home
Back to top