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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Dom0 has some schedulers, but that's not really relevant. If you understand type 1 vs type 2, then your statement here doesn't really make sense. I'm not sure what you are trying to say.

      Why isn't it relevant? You have a kernel booted up, containing a set of drivers and schedulers, then you have a management VM coming up containing it's own kernel, drivers and schedulers, and some of the system calls a VM executes will have to go through the Dom0's schedulers, to reach the DomU drivers and make syscalls and some will go to the DomU. And yes, some will go to Dom0, which will direct them to DomU (there was a diagram published about all that circa 2011 with the specific calls). How is that more efficient that a single set of schedulers?

      You can't just say "this is irrelevant" when it goes against the point you're trying to prove 🙂

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      You are circling back and ignoring what I've written. No, that's not enough to be an OS. I stated that explicitly a few times to make sure you'd not make this mistake, specifically about KVM. Kernel + "some stuff" isn't an OS on its own.

      Sorry but I don't take your word for that, you say it is a mistake, I say it is not. A missile guided by an RTOS or an older phone that could only do a few things, still had operating systems in them, it's just that the scope of those OS's was narrower than that of Linux or Windows. And it isn't "some stuff" (I'll thank you not to put words in my mouth), it is software that utilizes the interfaces the kernel exposes to a specific purpose.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      You'll have to excuse me for being skeptical, as claiming that Hyper-V is actually a type 2 (runs on Windows) is the stock example of misconceptions around Hyper-V since day one. This isn't a new claim, it's just one we've heard and seen disproven so many times. And it always ends up being the same things...

      I never said it was type 2, types are generally a dumb way of looking at hypervisors. If you have a hypervisor, it is a type 1 by definition, anything else is an emulator.

      But after going through this hundreds of times, it's always been the same thing. At some point, it's hard to take a new claim seriously.

      It is hard to take a claim of existing proof and documentation without seeing those. You claim something is true - be ready to prove it.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Can I prove it beyond the history and documentation and common sense? No. Can you prove that all industry knowledge, records, and vendor information from the time were falsified? I'm not saying it can't happen, I'm saying that it is rather absurd and the position of having the burden of proof lies with the person making the outrageous claim.

      Can you display those records you mentioned? That documentation?

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      It's not better, hence the point. Type 2 needs double the schedulers. Type 2 has the extra layers.

      No. Xen has schedulers in DomU and then Dom0 enforces additional schedulers of it's own. The same goes in Hyper-V. In KVM there is only one set of schedulers - the ones already existing and perfected over the years in the Linux kernel.

      KVM is type 1 because the hypervisor runs on bare metal. The definition is universal, it's not different for each thing. KVM is part of the Linux kernel which, as we established already, is not exclusively an OS kernel, and so KVM does not run on an OS.

      KVM is weird to discuss and very confusing because it is polymorphic. You can run KVM without an OS, or with an OS, but in both cases KVM is on the bare metal. KVM is unique in that no other hypervisor kernel is currently capable of being used as an OS kernel. Of course, any kernel could be in you added an OS to it, but no one does, that's silly. And that's why KVM is often seen as bloated, because it has those options and most people use them, at least to some degree. But at the end of the day, KVM is on the bare metal, end of story. And don't say it isn't, because it is. It's on bare metal in the way that the entire industry accepts the term. And it is that use of the term that defines the hypervisor type.

      KVM is a kernel module, which requires a kernel and some userspace software (wait, isn't that an OS?) to actually run a VM. You always need those. That's the entire point.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Relied on, but didn't run on. That's the common myth that started in that era. It was absolutely a type 1 at the time, and we were having these exact discussions at the time about how everyone thought it ran on top of Windows, but didn't. It's been improved since then, but being its own kernel and not running on the Windows one hasn't changed in that time.

      It still "relies on" the Windows kernel today, but only in the Dom0. The Windows kernel runs on top of the Hyper-V kernel, and always has.

      Can you prove that?

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      You are using the false term "OS Kernel" instead of the correct term "hypervisor or hypervisor kernel" making it seem like you didn't just say "not quite" while agreeing with what I said. DomU, or Xen, or the kernel (all the same thing) is what schedules the CPU. Thereby making it the very definition of bare metal. That it schedules its own tasks or the tasks of its helpers is exactly what bare metal means here.

      So now we have different kernels. OK, a kernel does not an OS make. We need a bit of software talking to the kernel to actually be an OS. Now lets see, the DomU is booted up, it loaded a bunch of interfaces that allow software access to the drivers enabling the execution of VMs. So far it's the kernel only. So what is it that started the Dom0, of not a utility software bundled with the DomU?

      Don't keep calling the hypervisor an "OS kernel", there is no purpose for that confusion. It's obviously not correct. And there is no reason for it except to avoid stating the obvious... that the hypervisor is what is running on the bare metal. Once you call it what it is, it's clear where it runs.

      An OS is a kernel and software utilizing that kernel to whatever purpose. Boot up ESXi, I'm sure you'll find more than just a kernel and a bunch of ABIs there.

      There is a reason why semantics is the most important part of communications. Get the semantics accurate, and most confusion tends to go away. It seems that it is only because of non-standard semantics that it seems confusing.

      Exactly why I keep saying the common baremetal pitch is wrong

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Sure. Because we define commodity hardware as not having that feature. Add that feature, to anything, and we stop calling it commodity.

      It isn't like virtualization is unique to commodity hardware. In the past, it was the one type that didn't have virtualization (hence why that market was left with a knowledge cap leading to confusion when it was suddenly introduced to something that the rest of IT had long ago standardized on and accepted.)

      I call standard x86 servers commodity. And you?

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      I've twisted nothing. And you aren't repeating that definition accurately. It's close, but modified just enough to make it not make sense. Type 1 runs directly ON the hardware, and there is nothing about if an assisting OS exists (that would be weird and makes no sense, hence your confusion.) If you use the standard definitions, it's all clear and sensible. It's your modification of them that makes it all seem crazy.

      Wait, you're saying an assisting OS doesn't exist? What is the DomU then? It is way more than just a driver for VT/SVM.

      Type 2 is definitely not as good as type 1 architecturally. More to fail, more layers. Type 2 has its place, but not for production workloads. It's really used for testing. Even there, it is losing popularity quickly.

      That's funny, having double the schedulers and double the drivers is better architecturally because..? And since we are there, how can you efine KVM to be type 1 if it uses an OS instead of implementing it's own set of schedulers and interfaces?

      I've not removed the CPU extensions, because they have never been relevant. They aren't part of any definition, and aren't needed for the conversation. You bring them up and by adding them in as part of your definitions make the simple, straightforward, and sensible definitions that everyone accepts and has accepted for decades seem crazy. If you don't inject a need for them into the definitions, suddenly the standard definitions are totally logical.

      CPU extensions are great, but at the end of the day, they are "helpers" and remain optional. A good option, but an option nonetheless.

      Without CPU extensions what you have is emulation (well, binary translation at best) which takes you even further from "baremetal".

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      I think you are thinking of Microsoft Virtual Server, not Hyper-V. Virtual Server was a type 2 hypervisor from MS that they used prior to Hyper-V. Hyper-V was bare metal (aka native, aka Type 1) from the start (2008.) While MS can apply the same name to two unrelated products (Windows 95 and Windows 2000), they rarely do and I am pretty sure that they did not with Hyper-V. Hyper-V was type 1 on its first day on the market.

      Nope, Hyper-V on 2008 and 2008R2 relied on the windows kernel, in 2012 it got separated into a separate kernel. Xen folks managed the overhaul, don't remember the names right now.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      I dont' agree here at all. People try to make terms fluid for some reason, but they are not. It's not loose English meaning "whatever people who don't know use them to mean", it is technical jargon and well known, documented, and clear.

      Baremetal is a very well established term and I've never once heard anyone not know what it meant before. Not across any community or media. It's not non-sense and is an extremely important term.

      It is nonsense in the way it is peddled by the major vendors' marketing teams. What they keep pouring into people's ears is what I've been explaining to the more junior IT folks to be wrong - baremetal is not software-free, on-hardware. Hypervisor types do not make sense (because if you ask a vmware salesman you'll hear the baremetal-not-baremetal argument right there). Nothing works on the hardware directly, everything goes through layers. A VM you start has to go through a layer to get CPU time, luckily it's just one layer, but you also need to get scheduled inside and outside the VM, so you'll have overhead (and gang scheduling if you paid for vmware 🙂 ). In short, there is no magic in virtualization, and saying something is "baremetal" does not make your VMs actually run on the real hardware.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Right, and this is what is wrong. If they did what you are describing, that's not bare metal, that's hardware virtualization (aka, IBM, Oracle, HPE implementation.)

      And it isn't available on commodity hardware.

      There IS true bare metal. It's how we all do it. You could argue that Xen and Hyper-V aren't bare metal, but that requires redefining bare metal hypervisors to do so. But KVM and ESXi have no possibility but being bare metal, there is nothing beneath them at all, and no helpers anywhere.

      Not quite. There is direct access to the CPU extensions, scheduled by the OS kernel (even if you prefer to call that OS vmkernel or DomU). And there is a ton of supporting software emulated stuff attached, because a VM is more than just a CPU.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Type 1 hypervisor means that the hypervisor itself runs without being "managed" by another layer of code, it is the "controlling" kernel that controls access to the CPU through scheduling.

      A Type 2 hypervisor gets scheduled by the OS it is running on top of. A type 2 hypervisor relies on the OS kernel that you describe.

      I still don't like the description (and the fact you managed to twist it quite a bit). The official description of the types is that type 1 works directly with the hardware without an assisting OS (which is absurd) and type 2 needs to go through an OS before it gets to the hardware. What you did here is basically remove the CPU extensions drivers and start talking about schedulers. Folks who don't know any better might even think type 2 (the way you describe it) isn't as good as type 1, because "schedulers".

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Virtualization proved to be beyond comprehension for a lot of IT, so misuse of terms was rampant. For example, most IT pros, even those in the Windows space, actually believe that Hyper-V is loaded on top of Windows and don't realize it is bare metal. Even explaining how it works, or showing that the load method is decades old and very standard, it's still super confusing. Or explaining that things like RDP is not a form of virtualization - because they RDP into virtual servers so the two must be the same thing, right?

      The early versions of hyper-v were loaded on top of windows actually. Later in the game, MS got tired of lagging behind so they hired some of the Xen folks to do a complete architectural rewrite. Now hyper-v works just like Xen. In fact, VMWare also rewrote their stuff to the same model more or less, when they moved from ESX to ESXi.

      So terms have gotten really murky when only looking at the most recent years where we've been immersed in misinformation. But these are all things that have been around a long time.

      Terms in IT are very fluid, true. This is exactly why I don't like the hypervisor types distinction, and this "baremetal" nonsense

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Okay, but now you are excluding other modern hypervisors. You have picked a subset of hypervisors particular to your use case that doesn't include Xen even now, and ignores the hypervisors from vendors like Oracle and IBM today. It's not modern vs. old, it's "things you are thinking of versus ones you aren't thinking about".

      Wrong. Xen is loading it's own stripped down kernel with a minimal set of features, aka domU (yes, a tiny little OS) which loads up dom0 to manage it all.

      Vbox (if that is what you meant) uses an OS and actually has it's own VT drivers nowadays.

      All I'm saying is that there is no real true baremetal, it's just not possible unless the stack is implemented in hardware, which isn't the case on commodity hardware.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Well, it's not very arguable. It's the accepted definition for decades. "An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. "

      I see no negation to needing to narrow down the functionality of the OS here.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Not at all. Hypervisors pre-date those features. It's redefining hypervisor after the fact that makes that seem plausible. But it's not. Hypervisors are not drivers, and hypervisors don't require CPU extensions. That's a very recent thing considering we've had hypervisors for many decades, but the extensions only for about fifteen years.

      OK, replace that with "modern hypervisor". I'm sure you know 15 years in IT is quite the eternity

      If you were in the virtualization and hypervisor world before that stuff existed, it would make it obvious how silly it is to say that hypervisors require something that is decades younger than they are.

      I was not, but I specialized in the modern version of virtualization for the past 10 years or so

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      It's all semantics. Semantics is just another term for accuracy. A kernel plus tools for a function has never been the description of an OS. An OS has to be a specific general purpose platform for applications. If you narrow the use, it has to stop being an OS.

      That is extremely arguable. Actually, my wife, a VHDL/VLSI/FPGA developer, would laugh if she heard that 🙂

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Except that all of those things go on the bare metal in type 1 systems. Hence why they are called bare metal hypervisors. (Except the utilities portion.)

      Nothing is on bare metal. It is all software loaded into memory by a kernel loaded after POST. The drivers work with the "baremetal" directly, everything else works through a driver, or is emulated in software. Does the VNC console to a Xen VM work on baremetal?

      And keep in mind that bare metal virtualization exists even without the hardware pieces you mentioned. Some of us come from the virtualization world prior to that stuff existing. In the SMB world these days, those tend to be considered foregone conclusions, but in the bigger sense, they are not. Xen, for example, predates that stuff by quite a bit, as does ESX.

      The only real baremetal VMs were on mainframes (and I suppose there might be some exotic FPGA implementations), but we're not discussing those right now.

      Most virtualization systems only provide an API on the bare metal, and put the management utilities for end users elsewhere. But that's not the hypervisor.

      API on the baremetal. Really. Can you show me the chip that API is implemented in?

      But the hypervisor... including the kernel, any drivers, and the hardware emulation sit on bare metal with all bare metal hypervisors.

      the hypervisor is part of the kernel, like all other hardware drivers. It IS a driver, for the CPU extensions. Exactly what I've been saying. Only the kernel isn't on baremetal, it's software that gets loaded by the BIOS and is the lowest level talking to the hardware.

      posted in IT Discussion
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    • RE: What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options

      @scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:

      Not an OS. An OS has a definition, and true hypervisors don't meet it. It's like an OS, yes. But it's different. KVM/Linux is unique in that depending on configuration it can be either or both.

      But remember, Linux isn't an OS, it's not enough on its own. It's only a kernel. It's a kernel meant for an OS, but that doesn't make it an OS.

      But Xen, Hyper-V, and ESXi don't contain kernels even meant for an OS.

      That's semantics. A kernel and a set of tools to perform a function, comprise an OS, maybe not a generic universal OS that can do anything, but an OS nonetheless. An RTOS that guides a rocket is tiny and very narrow in it's use, but it's an OS nonetheless. Like I said - semantics.

      A hypervisor is never a driver. To be a hypervisor, you must be a kernel. If it is only a driver, it's not a hypervisor. Or not a type 1, at least.

      Actually, a hypervisor in it's cleanest form is exactly that - a driver made to address the extra CPU features that allow for proper virtualization instead of tricks with optimized emulation, like VMWare did before VT. But nobody uses that word in that sense, because if we did - the only actual hypervisor out there would be KVM, all others are a stack of driver plus emulators, plus hardware drivers, schedulers and userspace tools.

      A type 2 hypervisor has a driver, but must be more than a driver to be the hypervisor.

      Hypervisor types have been made moot by KVM's emergence 12 years ago.

      posted in IT Discussion
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