XCP-ng Center 20.03.00 released
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So it's clear to me (as thinking of inside Center): it is not a "template", so the snapshot is not working in the VM creation wizard. That's also the case with XOA snaps from backups, you can not create a VM from that in Center.. I always wondered about that, but as you found the flag it seems clear to me.
We could fix it in two ways:
- let Center create VMs from also from snapshot that are not "a template"
- don't show the menu entry in Center on the snapshot list if it is not "is-template"
I wonder why this flag is important, what was the reason to program Center this way
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I would surmise, that since Center is behaving as it has for as long as I can remember, the fix should be applied to XO.
XO should set the template flag on a snapshot, so XenCenter and XCP-ng Center both behave as expected. The two flags I imagine are used by XenCenter and XCP-ng to build lists in the relevant dialogs that require ONLY templates, or templates and snapshots of a given VM. In this case, the dialog looks to show is-a-template (true) and is-a-snap-shot (true) and is it for the selected VM.
That said, I don't know enough about the implications. It may just be a flag, or there is something much deeper going on.
Said another way, if XO's snapshots are generated identically to Center's snapshots, then the flag is the only difference. The flag would be the only fix needed.
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We won't change a behavior on XO without having a good reason to do so. Historical reason is not a good one
Happy to learn more if it's relevant to anything 
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Said another way, if XO's snapshots are generated identically to Center's snapshots, then the flag is the only difference. The flag would be the only fix needed.
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"Fix needed" from your perspective, not for mine, until there's a good reason to do so
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Your response worries me. How many other features in Center, replicated in XO, are actually not the same feature? As a user, I trust that a snapshot in *Center or XO behave identically across both. They are both supposed to be using the same API. Why are they different? Over time, it would lead to distrust of XO.
I have just learned, for example, I cannot trust XO snapshots. And what problems might I encounter with VMs created in XO today, when I try to manage them in Center, months from now?
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Ask @nikade how he feels about some differences
We are trying to do things right, and with less "historical" reasons. Xen Orchestra is NOT a clone of XenCenter. And was never meant to be.If you are using XCP-ng, you should trust XO more than XCP-ng Center: because XO is actively maintained by a team of 6 dev working full time. XCP-ng Center is kindly maintained by @borzel and he's alone.
Also, you can't tell us it's a move from us to make people prisoner about a product, Xen Orchestra is fully Open Source and free.
So if you can explain the reason why we should do otherwise about snapshot, go ahead. Otherwise, I won't change a XO behavior without any other reason that's how another client is doing: this is not enough.
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I understand your point, but my point is just as valid: I have just learned, for example, I cannot trust XO snapshots. And what problems might I encounter with VMs created in XO today, when I try to manage them in Center, months from now?
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Why you can't trust them?
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Because they are not true snapshots, as they have been defined in Center. They do not behave the same, then they are not the same. Yet they are both snapshots... What else is called the same in XO and Center but are actually not the same?
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WTF, "not true snapshots"? Best I've heard today
Seriously, try to understand why on earth XCP-ng Center is doing that instead of telling it's XO's fault.
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It is doing that because upstream does that.
A true snapshot allows me to create a VM from it. It has done so in XenCenter for as long as I can remember, and XCP-ng Center has continued that.
And yes, this makes me very weary of using XO, and that I will not have a choice in the future but XO.
But, I will leave now and you can decide how much it is ok to diverge from upstream.
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There's no true or false snapshot: there's snapshot that's a template, which is dumb because if you export the snapshot then it's a template and not a VM.
In XO, a snapshot is a VM, not a template. Which is far better. For tons of reasons: backup/restore, export etc.
Now convince me we should do otherwise, for now you have 0 technical argument.
edit: if you like that much what you call the "upstream" (real thing would be more "the original"), why are you using XCP-ng and not Citrix Hypervisor?
In XCP-ng, upstream is where there's more contribution. XO get more than XCP-ng Center, so it's the only officially supported client or XCP-ng.
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I am using XCP-ng because I believe in your vision as opposed to your competitors. There are other options, and yet I like what you've done with XO/A and XCP-ng. And that's why I am writing here, whereas I have never participated in a feature/bug discussion with Citrix.
If earn a Euro in France, I expect that Euro to behave the same anywhere else that Euro's are accepted. I didn't earn a French Euro, only valid in places that accept French Euros.
The snapshot I created in XO, is my earned Euro. Except that I didn't realize it was an XO Snapshot, different from a Center snapshot. Why that is I leave to you, but it is undeniable that they are not created equal, be it a dumb concept or not.
Still, there is no need to continue this, as the facts are already in the thread, from both perspectives. I was just trying to help, and I am learning more than I ever expected.
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That's what I thought, you don't really get the fact it's still a snapshot.
It's just that it's not a template, which is only a flag to tell XAPI how to behave. It comes with the exact same data inside.
These are the facts. That you don't like it is an opinion, not a fact
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No, I get that... and thats the silly part. All XO needs to do is set the flag, and it has been clear from the moment you had me print the objects.
It is super clear to me... the XO Snapshot is different than the Center Snapshot, only because of a single flag that XO is not setting to be true.
That difference, is enough to make them behave differently. They are not the same, no matter how tiny that difference may be.
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All XO needs to do is set the flag
You have 0 knowledge about how it works underneath there and why we did the change. I already explained why. Please read my post carefully.
So far, 0 technical argument about why we should change this behavior and why it's not the opposite (XenCenter should change this)
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I appreciate you trying to educate me. However, we're going in circles... Its ok, I get it. The end result is:
- XO Snapshots are, by example, different than Center Snapshots, by a single flag.
- Once Center goes away, XO Snapshots will be the only snapshots.
- No issue here
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I can reverse the sentence: XCP-ng Center snapshots are using
is a templateat true, unlike than those done on the only officially supported client, XO.In XO, the reason to do so is the fact those snapshot are directly bootable VMs than you can revert or export. But you can also convert them into a template in the XO UI.
Having this kind of snapshot (not with template at true) is also a basic feature allowing backups, so you can restore your backup without having a template instead.
I don't see any valid reason to change that behavior in XO.
