In MAAS, you can define the disk layout, either flat or Logical Volume Manager
(LVM), as well as the partitioning schema per server.
This section describes how to define these parameters in the MAAS section
of the MCP model.
The disk configuration applies during the deployment process.
If you want to define the disk configuration after deployment,
you can use salt-formula-linux that also has a capability to set up LVM
partitioning. But the whole definition for each Volume Group must be either
in the maas or linux section, since the linux state cannot
override or extend an existing Volume Group created using MAAS but can create
a new one.
Caution
You can define the disk configuration in the model before the
deployment starts. But be aware that enforcing of this
configuration to MAAS using the salt state must be done
after servers are commissioned and before they are deployed.
Basically, maas.machines.storage works only if a server
is in the READY state.
Caution
The maas.machines.storage state overlaps with
the linux.storage state. Therefore, we recommend using
only one of them. If your deployment requires both, be aware that:
The linux.storage configuration must match the
maas.machines.storage configuration.
MAAS may use an inexplicit mapping.
For example, the following MAAS configuration will create
an inexplicit mapping to sda1. And this specific sda1
device must be defined in the linux.storage configuration.
maas:
...
vg0:
type: lvm
devices:
- sda
...
You can use several options to design the disk layout in a deployment depending on specific use cases. This section includes three most common examples that can be combined to get your desired configuration.
To define a different disk layout with custom parameters
The default layouts used by MAAS are flat and Logical Volume Manager (LVM). Flat layout creates a root partition on the first disk of a server. LVM creates a Volume Group on this partition with one volume per root. By default, in both types of disk layout, the entire space on the first disk is used. If you want to change this behavior, redefine the disk layout parameters.
The following examples illustrate a modified configuration of the default values for partition size as well as LVM names for Volume Group and Logical Volume:
Flat layout:
maas:
region:
machines:
server1:
disk_layout:
type: flat
root_size: 10G #sda disk has more then 10G
root_device: sda
bootable_device: sda
LVM layout:
maas:
region:
machines:
server1:
disk_layout:
type: lvm
root_size: 20G #sda disk has more then 20G
root_device: sda
bootable_device: sda
volume_group: vg0
volume_name: root
volume_size: 10G #If not defined, whole root partition is used.
Caution
When defining the disk layout in the model, do not modify
the rest of the disk using the MAAS dashboard.
Each run of maas.machines.storage deletes and recreates
the disk configuration of a server.
Currently, this state is not idempotent.
To define a custom partitioning schema
To define a more complex configuration for disks, use the disk section
under the disk_layout parameter.
The following example illustrates how to create partitions on the sda disk
and a Volume Group with Logical Volumes on the sdb disk.
Be aware that sdb is also defined without any partitioning schema.
Therefore, you can enforce no partition to be present on sdb.
Also, due to the volume_group1 dependency on this device,
it must be defined with some configuration in the model.
In the example below, it has no partitioning schema.
Example of creating partitions and Logical Volumes:
maas:
region:
machines:
server3:
disk_layout:
type: custom
bootable_device: sda
disk:
sda:
type: physical
partition_schema:
part1:
size: 10G
type: ext4
mount: '/'
part2:
size: 2G
part3:
size: 3G
sdb:
type: physical
volume_group1:
type: lvm
devices:
- sdb
volume:
tmp:
size: 5G
type: ext4
mount: '/tmp'
log:
size: 7G
type: ext4
mount: '/var/log'
Caution
The naming convention for partition in MAAS does not allow
using custom names. Therefore, key names in YAML for partition
are always part1, part2, …, partN.
To define the software RAID
Using the disk section from the previous example, you can create
the software RAID on servers. You can use this device for LVM or
you can define a partitioning schema directly on this device.
The following example illustrates how to create raid 1 on sda and
sdb with the partitioning schema. In this example, we use flat layout
that creates a root partition on sda, but this partition is eventually
deleted because sda is defined without any partitioning schema.
Example of creating the software RAID disks:
maas:
region:
machines:
server3:
disk_layout:
type: custom
bootable_device: sda
disk:
sda:
type: physical
sdb:
type: physical
md0:
type: raid
level: 1
devices:
- sda
- sdb
partition_schema:
part1:
size: 10G
type: ext4
mount: '/'
part2:
size: 5G
part3:
size: 25G
To apply changes to MAAS
To enforce the disk configuration on servers in MAAS, run the maas state
on a node where the MAAS model is included. Usually, this is the cfg01
node.
salt-call state.sls maas.machines.storage
Now, proceed with the MCP deployment depending on your use case as described in Provision physical nodes using MAAS.