On Thu, 2024-04-18 at 10:39 +0000, Andy Smith via BitFolk Users wrote:
Hi,

We had a customer ask about backups of images of their VM disk. This
is not currently a service that we offer.

It has some advantages, so it could be a service that we offer.
The main advantage being:

- High degree of confidence that the VM is just able to be one-click
  restored and is then bootable and working, as it's an exact image
  of the disk

It does of course also have a heap of disadvantages such as:

- Granularity of backup is "the entire disk". No way to pick and
  choose what is backed up except by putting things on different OS
  disks.

- It's based off a disk snapshot so nothing in memory gets
  preserved; a restore event will be similar to a "boot after
  unexpected power cut" event to the restored VM. Though doing the
  snapshot while the VM is powered off for a few seconds would be
  an option.

- This obviously uses a lot of disk space which we'd charge for at
  our archive storage rate: £0.40+VAT/50GB/month. If preferred this
  could go onto third party cloud storage but bear in mind that
  Amazon S3 is about 3 times the cost of BitFolk's archive storage.

- Limited differential backups are possible though I'm yet to fully
  understand how well that works. All I can say right now is that
  a differential would use less, but I'm not sure really how much
  less.

So, there would be "some charge" for the service itself and
definitely a charge at archive storage rates for the actual amount
of storage involved.

If this sounds like a service that you think you'd actually want,
please get in touch off-list and we'll see if we can develop it.

As it's more the BitFolk way for customers to do this sort of thing
themselves I don't really expect this to be widely desired, but I am
working on it for one customer anyway so if I can make it more
generally applicable then I will.

Thanks,
Andy


Hi,

I would find this useful. I would store such images at home on my cheap disks. My usecase would be something like this:
1) trigger image via http/wget/curl/API
2) poll for it be completed
3) download image
4) delete image (via some api)

That would be very useful for me indeed and would not require storage/archive at bitfolk. To restore an image, some sort of upload would need to be available, but that is secondary for my case, since, with the image, I can get to the filesystem and restore files if necessary.

As per 'snapshot' - I am not certain about xen, but did a lot with qemu/kvm. the "live migration" feature essentially gives you a consistent view of disk+memory+devicestate that one can store. The image(s) then are equivalent to starting a running machine. I wonder if xen does something like that as well.

Also to ponder: It might be possible to send the VM to a "sleep" state for something like 5s, to get a consistent snapshot of disk and memory.

Conrad