Storage¶

This page describes standard and custom storage layouts available in MAAS.

Standard storage layouts¶

The layout descriptions below will include the EFI partition. If your system is not using UEFI, regard sda2 as sda1 (with an additional 512 MB available to it).

Flat layout¶

With the Flat layout, a partition spans the entire boot disk. The partition is formatted with the ext4 filesystem and uses the / mount point:

Name	Size	Type	Filesystem	Mount point
sda	-	disk
sda1	512 MB	part	FAT32	/boot/efi
sda2	rest of sda	part	ext4	/

The following three options are supported:

boot_size: Size of the boot partition on the boot disk. Default is 0, meaning not to create the boot partition. The ‘/boot’ will be placed on the root filesystem.
root_device: The block device on which to place the root partition. The default is the boot disk.
root_size: Size of the root partition. Default is 100%, meaning the entire size of the root device.

LVM layout¶

The LVM layout creates the volume group vgroot on a partition that spans the entire boot disk. A logical volume lvroot is created for the full size of the volume group; is formatted with the ext4 filesystem; and uses the / mount point:

Name	Size	Type	Filesystem	Mount point
sda	-	disk
sda1	512 MB	part	FAT32	/boot/efi
sda2	rest of sda	part	lvm-pv(vgroot)
lvroot	rest of sda	lvm	ext4	/
vgroot	rest of sda	lvm

The following six options are supported:

boot_size: Size of the boot partition on the boot disk. Default is 0, meaning not to create the boot partition. The ‘/boot’ will be placed on the root filesystem.
root_device: The block device on which to place the root partition. The default is the boot disk.
root_size: Size of the root partition. Default is 100%, meaning the entire size of the root device.
vg_name: Name of the created volume group. Default is vgroot.
lv_name: Name of the created logical volume. Default is lvroot.
lv_size: Size of the created logical volume. Default is 100%, meaning the entire size of the volume group.

bcache layout¶

A bcache layout will create a partition that spans the entire boot disk as the backing device. It uses the smallest block device tagged with ‘ssd’ as the cache device. The bcache device is formatted with the ext4 filesystem and uses the / mount point. If there are no ‘ssd’ tagged block devices on the machine, then the bcache device will not be created, and the Flat layout will be used instead:

Name	Size	Type	Filesystem	Mount point
sda	-	disk
sda1	512 MB	part	FAT32	/boot/efi
sda2	rest of sda	part	bc-backing
sdb (ssd)	-	disk
sdb1	100% of sdb	part	bc-cache
bcache0	per sda2	disk	ext4	/

The following seven options are supported:

boot_size: Size of the boot partition on the boot disk. Default is 0, meaning not to create the boot partition. The ‘/boot’ will be placed on the root filesystem.
root_device: The block device upon which to place the root partition. The default is the boot disk.
root_size: Size of the root partition. Default is 100%, meaning the entire size of the root device.
cache_device: The block device to use as the cache device. Default is the smallest block device tagged ssd.
cache_mode: The cache mode to which MAAS should set the created bcache device. The default is writethrough.
cache_size: The size of the partition on the cache device. Default is 100%, meaning the entire size of the cache device.
cache_no_part: Whether or not to create a partition on the cache device. Default is false, meaning to create a partition using the given cache_size. If set to true, no partition will be created, and the raw cache device will be used as the cache.

vmfs6 storage layout reference

VMFS6 layout¶

The VMFS6 layout is used for VMware ESXi deployments only. It is required when configuring VMware VMFS Datastores. This layout creates all operating system partitions, in addition to the default datastore. The datastore may be modified. New datastores may be created or extended to include other storage devices. The base operating system partitions may not be modified because VMware ESXi requires them. Once applied another storage layout must be applied to remove the operating system partitions.

Name	Size	Type	Use
sda	-	disk
sda1	3 MB	part	EFI
sda2	4 GB	part	Basic Data
sda3	Remaining	part	VMFS Datastore 1
sda4	-	skipped
sda5	249 MB	part	Basic Data
sda6	249 MB	part	Basic Data
sda7	109 MB	part	VMware Diagnostic
sda8	285 MB	part	Basic Data
sda9	2.5 GB	part	VMware Diagnostic

The following options are supported:

root_device: The block device upon which to place the root partition. Default is the boot disk.
root_size: Size of the default VMFS Datastore. Default is 100%, meaning the remaining size of the root disk.

Blank layout¶

The blank layout removes all storage configuration from all storage devices. It is useful when needing to apply a custom storage configuration.

Machines with the blank layout applied are not deployable; you must first configure storage manually.

Custom storage layouts¶

This section provides examples of commonly-used custom storage layouts for MAAS-deployed machines. These examples provide custom storage layout configurations that a script could output to the $MAAS_STORAGE_CONFIG_FILE. For clarity, this section assumes that the machine has 5 disks (named sda to sde); be sure to adjust accordingly.

There is no need to add entries for those devices in the layout section if the disks are not explicitly partitioned, but just used by other devices (e.g. RAID or LVM).

GPT partitioning¶

Here is an example of a simple single-disk layout with GPT partitioning.

{
  "layout": {
    "sda": {
      "type": "disk",
      "ptable": "gpt",
      "boot": true,
      "partitions": [
        {
          "name": "sda1",
          "fs": "vfat",
          "size": "500M",
          "bootable": true
        },
        {
          "name": "sda2",
          "size": "5G",
          "fs": "ext4"
        },
        {
          "name": "sda3",
          "size": "2G",
          "fs": "swap"
        },
        {
          "name": "sda4",
          "size": "120G",
          "fs": "ext4"
        }
      ]
    }
  },
  "mounts": {
    "/": {
      "device": "sda2",
      "options": "noatime"
    },
    "/boot/efi": {
      "device": "sda1"
    },
    "/data": {
      "device": "sda4"
    },
    "none": {
      "device": "sda3"
    }
  }
}

In the mounts section, options for mount points can be specified. For swap, an entry must be present (with any unique name that doesn’t start with a /), otherwise the swap will be created but not activated.

RAID 5¶

This example describes the reference setup for a RAID 5 configuration with spare devices.

{
  "layout": {
    "storage": {
      "type": "raid",
      "level": 5,
      "members": [
        "sda",
        "sdb",
        "sdc"
      ],
      "spares": [
        "sdd",
        "sde"
      ],
      "fs": "btrfs"
    }
  },
  "mounts": {
    "/data": {
      "device": "storage"
    }
  }
}

Both full disks and partitions can be used as RAID members.

Pre-defined LVM¶

In this reference example, you can find an LVM with pre-defined volumes.

{
  "layout": {
    "storage": {
      "type": "lvm",
      "members": [
        "sda",
        "sdb",
        "sdc",
        "sdd"
      ],
      "volumes": [
        {
          "name": "data1",
          "size": "1T",
          "fs": "ext4"
        },
        {
          "name": "data2",
          "size": "2.5T",
          "fs": "btrfs"
        }
      ]
    }
  },
  "mounts": {
    "/data1": {
      "device": "data1"
    },
    "/data2": {
      "device": "data2"
    }
  }
}

If no volumes are specified, the volume group is still created.

Bcache¶

Here is an example of a custom bcache setup.

{
  "layout": {
     "data1": {
      "type": "bcache",
      "cache-device": "sda",
      "backing-device": "sdb",
      "cache-mode": "writeback",
      "fs": "ext4"
    },
    "data2": {
      "type": "bcache",
      "cache-device": "sda",
      "backing-device": "sdc",
      "fs": "btrfs"
    }
  },
  "mounts": {
    "/data1": {
      "device": "data1"
    },
    "/data2": {
      "device": "data2"
    }
  }
}

The same cache set can be used by different bcaches by specifying the same backing-device for them.

LVM RAID with bcache¶

This more complex reference example describes an LVM on top of RAID with bcache enabled for read-intensive operations.

{
  "layout": {
    "bcache0": {
      "type": "bcache",
      "backing-device": "sda",
      "cache-device": "sdf"
    },
    "bcache1": {
      "type": "bcache",
      "backing-device": "sdb",
      "cache-device": "sdf"
    },
    "bcache2": {
      "type": "bcache",
      "backing-device": "sdc",
      "cache-device": "sdf"
    },
    "bcache3": {
      "type": "bcache",
      "backing-device": "sdd",
      "cache-device": "sdf"
    },
    "bcache4": {
      "type": "bcache",
      "backing-device": "sde",
      "cache-device": "sdf"
    },
    "raid": {
      "type": "raid",
      "level": 5,
      "members": [
        "bcache0",
        "bcache1",
        "bcache2"
      ],
      "spares": [
        "bcache3",
        "bcache4"
      ]
    },
    "lvm": {
      "type": "lvm",
      "members": [
        "raid"
      ],
      "volumes": [
        {
          "name": "root",
          "size": "10G",
          "fs": "ext4"
        },
        {
          "name": "data",
          "size": "3T",
          "fs": "btrfs"
        }
      ]
    }
  },
  "mounts": {
   "/": {
      "device": "root"
    },
    "/data": {
      "device": "data"
    }
  }
}

The RAID is created by using 5 bcache devices, each one using a different disk and the same SSD cache device. LVM is created on top of the RAID device and volumes are then created in it, to provide partitions.