Debian 12 Cloud-Init VM: Which Cloud Init Image to Use?

[SInisterPisces]

Hello,

I'm following a tutorial for this, and it's awesome, but one of the things they didn't mention is which format of image to download between qcow2, raw, and tar.xz.

These are my choices:



My VM storage is local on the Proxmox node. It's a ZFS mirror on a pair of NVME. The storage itself is thin provisioned. Space is not a concern.
When I make a new VM manually (with no template or Cloud-Init), my only option for saving VM disks is "Raw", but I'm not sure how relevant that is.

I feel like RAW will always work (or can be converted? but I'm just guessing on that…), and I'm not too concerned about the space requirement.

Here's the setup for my storage:

  22   │ zfspool: vmStore64k
  23   │     pool rpool/data/vmStore64k
  24   │     blocksize 64k
  25   │     content images
  26   │     mountpoint /rpool/data/vmStore64k
  27   │     sparse 1

 

[mariol]

You can use both. Raw and qcow2. Both can be easily imported into your Zpool. For example:

qm importdisk <vmid> <path to your downloaded image> <your target zpool>

 

[bbgeek17]

If you are trying to preserve bandwidth and/or space, you can also download the xz file (which is the smallest of all), then decompress and untar it to a raw image:
xz -d debian-12-generic-arm64.tar.xz
tar tvf debian-12-generic-arm64.tar
-rw-r--r-- root/root 2147483648 2024-12-01 05:19 disk.raw

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Blockbridge: Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[SInisterPisces]

Thanks! I'm excited to try this.

So, just to double check (and because it's early enough here that I haven't had my tea yet), there's no functional difference between them?

 

[bbgeek17]

So, just to double check (and because it's early enough here that I haven't had my tea yet), there's no functional difference between them?

There is a functional difference. One is stored as raw blocks, the other uses QCOW format, the context is the same.

If you are doing an import, you will have a chance to convert between formats, i.e. raw>qcow, qcow>raw, or keep the format as is.

You also have a choice of simply "sliding in" the image to the appropriate location, if you are using file-based storage pool. In that case you will be "stuck" with chosen format until you decide to change it.
Qcow can provide on-disk compression and snapshots. Raw is faster, however, you may not notice the difference based on your CPU/Disk configuration.

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Blockbridge: Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[SInisterPisces]

Thanks again.

I think I'm all set.