Showing the size of a custom block volume

1

It seems odd that neither “incus storage volume show” nor “incus storage volume info” shows the size of a custom block volume (in incus 6.0.2 with zfs storage pool)

$ incus storage volume create zfs testblk --type=block
Storage volume testblk created
$ incus storage volume show zfs testblk
config: {}
description: ""
name: testblk
type: custom
used_by: []
location: none
content_type: block
project: nsrc-builder
created_at: 2024-09-30T10:12:46.832973731Z
$ incus storage volume info zfs testblk
Name: testblk
Type: custom
Content type: block
Usage: 12.00KiB
Created: 2024/09/30 10:12 UTC

To find its size, I looked at the raw zvol properties:

# zfs get all zfs0/lxd/custom/nsrc-builder_testblk
NAME                                  PROPERTY              VALUE                  SOURCE
...
zfs0/lxd/custom/nsrc-builder_testblk  volsize               10G                    local

Am I missing some other option within incus?

EDIT: I also get blank output from this command:

$ incus storage volume get zfs testblk size
$

Although one of the examples given by incus storage volume get --help shows:

Description:
  Get values for storage volume configuration keys
...

Examples:
  incus storage volume get default data size
      Returns the size of a custom volume "data" in pool "default"
2

Interestingly, after growing the volume I can see the size:

$ incus storage volume set zfs testblk size=11GiB
$ incus storage volume get zfs testblk size
11GiB

$ sudo zfs get volsize zfs0/lxd/custom/nsrc-builder_testblk
NAME                                  PROPERTY  VALUE    SOURCE
zfs0/lxd/custom/nsrc-builder_testblk  volsize   11G      local

I guess that when I was creating a volume with the default size, that the size was not recorded as part of its config? Perhaps it should be?

3

Default size for all block volumes is 10GiB, that’s why VMs get a 10GiB disk out of the box, similarly with no size config set.

4

I understand that if you create a block volume and don’t specify the size, it gets created as 10GiB. I was surprised that if you ask for information about the volume, it doesn’t say what size it is. It’s saying “I don’t have any size, therefore you have to assume I am whatever the default size is”.

What if the default size changes after the volume is created? (It’s not likely that a future version of incus will change the default volume size, but it’s not impossible either)

I can set a default volume size myself on the pool:

incus storage volume create --type=block zfs vol1
incus storage set zfs volume.size=15GiB
incus storage volume create --type=block zfs vol2

# zfs get volsize zfs0/lxd/custom/nsrc-builder_vol1
NAME                               PROPERTY  VALUE    SOURCE
zfs0/lxd/custom/nsrc-builder_vol1  volsize   10G      local

# zfs get volsize zfs0/lxd/custom/nsrc-builder_vol2
NAME                               PROPERTY  VALUE    SOURCE
zfs0/lxd/custom/nsrc-builder_vol2  volsize   15G      local

$ incus storage volume show zfs vol1
config: {}
description: ""
name: vol1
type: custom
used_by: []
location: none
content_type: block
project: nsrc-builder
created_at: 2024-10-02T07:47:40.208690269Z

$ incus storage volume show zfs vol2
config:
  size: 15GiB
description: ""
name: vol2
type: custom
used_by: []
location: none
content_type: block
project: nsrc-builder
created_at: 2024-10-02T07:48:16.893992996Z

Ah, so the config.size is stored in the volume if it was created with a non-default size. ISTM it would be clearer if the volume size were always stored.

However, now I understand this issue, I can set an explicit default volume size of 10GiB on the pool, and that is propagated to volumes:

incus storage set zfs volume.size=10GiB
incus storage volume create --type=block zfs vol3

$ incus storage volume show zfs vol3
config:
  size: 10GiB
description: ""
name: vol3
type: custom
used_by: []
location: none
content_type: block
project: nsrc-builder
created_at: 2024-10-02T07:53:07.312067572Z