One of the key elements of managing machines is configuring and managing their storage space. This subsection will help you learn:
- About block devices
- About partitions
- About storage restrictions
- About VMFS datastores
- About UEFI booting
- About final storage modifications
The Storage tab on the machine list brings up a form that allows you to view/edit the file system, partitioning and storage parameters for the selected machine:
This tab describes the filesystem(s) in use, as well as the available and used partitions for this machine.
About block devices
Once the initial storage layout has been configured on a machine, you can perform many operations to view and adjust the entire storage layout for the machine. In MAAS there are two different types of block devices.
Physical
A physical block device is a physically attached block device such as a 100GB hard drive connected to a server.
Virtual
A virtual block device is a block device that is exposed by the Linux kernel when an operation is performed. Almost all the operations on a physical block device can be performed on a virtual block device, such as a RAID device exposed as md0.
About partitions
As with block devices (see Block devices), MAAS and the MAAS API offer a great deal of control over the creation, formatting, mounting and deletion of partitions.
About storage restrictions
There are three restrictions for the storage configuration:
- An EFI partition is required to be on the boot disk for UEFI.
- You cannot place partitions on logical volumes.
- You cannot use a logical volume as a Bcache backing device.
Violating these restrictions will prevent a successful deployment.
About VMFS datastores
MAAS can configure custom local VMware VMFS Datastore layouts to maximise the usage of your local disks when deploying VMware ESXi. As VMware ESXi requires specific partitions for operating system usage, you must first apply the VMFS6 storage layout. This layout creates a VMFS Datastore named datastore1 which uses the disk space left over on the boot disk after MAAS creates the operating system partitions.
About UEFI booting
Every layout type supports a machine booting with UEFI. In such a case, MAAS automatically creates an EFI boot partition (/boot/efi). Other than setting the machine to boot from UEFI, the user does not need to take any additional action.
UEFI must be enabled or disabled for the lifespan of the machine. For example, do not enlist a machine with UEFI enabled, and then disable it before commissioning. It won’t work!
The EFI partition, if created, will be the first partition (sda1) and will have a FAT32 filesystem with a size of 512 MB.
About final storage modifications
Once MAAS provisions a machine with block devices, via a layout or administrator customisation, a regular user can modify the resulting storage configuration at the filesystem level.
About disk erasure
Disk erasure pertains to the erasing of data on each of a machine’s disks when the machine has been released (see Release action) back into the pool of available machines. The user can choose from among three erasure types before confirming the Release action, and a default erasure configuration can also be set. This section will help you learn:
- About disk erasure types
- About standard erasure
- About secure erasure
- About quick erasure
- About erasure order of preference
About disk erasure types
The three disk erasure types are:
- Standard erasure
- Secure erasure
- Quick erasure
Each of these are explained below.
About standard erasure
Overwrites all data with zeros.
About secure erasure
Although effectively equivalent to Standard erase, Secure erase is much faster because the disk’s firmware performs the operation. Because of this, however, some disks may not be able to perform this erasure type (SCSI, SAS, and FC disks in particular).
About quick erasure
Same as Standard erase but only targets the first 1 MB and the last 1 MB of each disk. This removes the partition tables and/or superblock from the disk, making data recovery difficult but not impossible.
About erasure order of preference
If all three options are checked when the machine is released, the following order of preference is applied:
- Use ‘secure erase’ if the disk supports it
- If it does not, then use ‘quick erase’