Devmapper storage for Slicer

Devmapper is one of the options for storage with Slicer.

We generally recommend using disk images for long-running VMs, or ZFS for launching many short-lived VMs.

That said, you can install Devmapper as an alternative, with a backing drive set up for it, just like we do for ZFS.

Installation

The setup for Devmapper is different to ZFS, you will need to run the installation script again, but this time, with additional arguments.

First, install a drive, or make a partition available for Devmapper to use.

Run lsblk to identify your drives.

$ lsblk
NAME                             MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
nvme1n1                          259:0    0 931.5G  0 disk 
├─nvme1n1p1                      259:1    0     1G  0 part /boot/efi
├─nvme1n1p2                      259:2    0     2G  0 part /boot
└─nvme1n1p3                      259:3    0 928.5G  0 part 
  └─ubuntu--vg-ubuntu--lv        253:0    0   500G  0 lvm  /
nvme0n1                          259:4    0   1.8T  0 disk 

In this instance, you can see that my 2TB NVMe SSD is called nvme0n1 and is currently not allocated.

Head over to the installation page and run the installation script again, this time include the VM_DEV environment variable.

The default size for any unpacked VM is 30GB, so if you want to alter that size do it now.

(
cd agent
BASE_SIZE=35GB VM_DEV=/dev/nvme0n1 sudo -E ./install.sh
)

Be very careful that you specify the correct drive or partition. This operation cannot be reserved, and will destroy any existing contents.

Configure Slicer to use Devmapper

config:
  host_groups:
  - name: vm
-   storage: image
-   storage_size: 25G
+   storage: devmapper

The storage_size field cannot be specified for Devmapper. So whatever size was setup for snapshots during the installation will be the size used for all VMs.