What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options
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@scottalanmiller of course, PV simply adds some shortcuts in (mainly) the IO path, assisted by a special driver in the guest. VirtIO is pretty much the same, and it's not exclusive to KVM any longer
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@dyasny said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
In fact, KVM was invented when an engineer working on Xen thought the architecture was flawed and overbloated, and things could have been done better. That engineer is my current CTO
It's a good idea, but one that hasn't proven to make all that much of a difference. In reality, what KVM ended up doing was splitting the community too far making the Xen / KVM world much weaker than it should have been with engineering and customer efforts split, rather than unified. Either approach works fine. KVM's is slightly better on paper, Xen was already good enough in practice. KVM is simpler, but not simpler enough to justify creating two competing ecosystems. Now things like XO that would have been amazing to have had with KVM are only for Xen, and things like CBD that are amazing for KVM don't exist for Xen. Imagine if all that effort was put into one project!
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@dyasny said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
@scottalanmiller of course, PV simply adds some shortcuts in (mainly) the IO path, assisted by a special driver in the guest. VirtIO is pretty much the same, and it's not exclusive to KVM any longer
You are thinking of PV Drivers, like KVM, ESXi, and Hyper-V use. No driver needed for full PV like Xen has. Instead, the entire kernel has to be recompiled for it!
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@scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
It's a good idea, but one that hasn't proven to make all that much of a difference. In reality, what KVM ended up doing was splitting the community too far making the Xen / KVM world much weaker than it should have been with engineering and customer efforts split, rather than unified. Either approach works fine. KVM's is slightly better on paper, Xen was already good enough in practice. KVM is simpler, but not simpler enough to justify creating two competing ecosystems. Now things like XO that would have been amazing to have had with KVM are only for Xen, and things like CBD that are amazing for KVM don't exist for Xen. Imagine if all that effort was put into one project!
A lot of the development went into QEMU and its various subprojects (virtio especially), and QEMU is utilized by both systems. But in any case, KVM is native to Linux, while Xen is a separate, foreign kernel that will never be a part of Linux. So, IMO, things would be better suited completely switched to KVM, instead of people insisting on sticking with Xen.
On the other hand, when you have a newer, better, faster and much more Linux-native design, why dump it just to keep the community effort in one place? Especially when Xen got scooped up by Citrix, a company that was never known for it's benevolence and support for the OSS community? I think everything took it's natural course, with Xen getting phased out by KVM as soon as feature parity was reached, and then easily surpassed in terms of uptake and installbase
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I want to know how old this table is, because I think that it is out of date.
https://wiki.xen.org/images/thumb/4/4b/XenHVM-All.png/700px-XenHVM-All.png
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@scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
You are thinking of PV Drivers, like KVM, ESXi, and Hyper-V use. No driver needed for full PV like Xen has. Instead, the entire kernel has to be recompiled for it!
But the kernel is, essentially, a blob of drivers
whether you compile or install modules, you get a new set of drivers in the end -
@dyasny said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
But in any case, KVM is native to Linux, while Xen is a separate, foreign kernel that will never be a part of Linux. So, IMO, things would be better suited completely switched to KVM, instead of people insisting on sticking with Xen.
Had KVM been the original project, I would agree completely. But I'm not sure that sharing the Linux kernel for two different purposes is best. It seems to come with a lot of benefits, but a lot of negatives, too. There is a reason that no one else goes down that path for this.
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I think Xen's future is to follow ESXi's path. Removing the Dom0, growing the kernel, and moving to limited, enterprise only, hardware support.
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@scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
Had KVM been the original project, I would agree completely. But I'm not sure that sharing the Linux kernel for two different purposes is best. It seems to come with a lot of benefits, but a lot of negatives, too. There is a reason that no one else goes down that path for this.
ESXi went down that path, didn't they? Nobody else[1] did because KVM is already there and available, all you need is to build a suitable kernel and maybe your own take on QEMU (like Amazon did).
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@scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
I think Xen's future is to follow ESXi's path. Removing the Dom0, growing the kernel, and moving to limited, enterprise only, hardware support.
I'm pretty sure they don't have the resources to do that. Nor is there any need - Xen as a commercial offering isn't anything to write home about, and as opensource, there isn't much demand for a slim hypervisor-only OS without cluster-level management abilities. Citrix might do something like that for the same reasons ESXi is available for free - as a first dose to get people hooked, but I'm not sure they can or want to invest so much in such an offering.
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@dyasny said in 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:
Had KVM been the original project, I would agree completely. But I'm not sure that sharing the Linux kernel for two different purposes is best. It seems to come with a lot of benefits, but a lot of negatives, too. There is a reason that no one else goes down that path for this.
ESXi went down that path, didn't they? Nobody else[1] did because KVM is already there and available, all you need is to build a suitable kernel and maybe your own take on QEMU (like Amazon did).
Hyper-V and Xen made separate kernels, but not their own driver sets.
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@scottalanmiller oh there are SOME drivers in those separate kernels, else they wouldn't be able to work at all.
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@dyasny said in 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 Xen's future is to follow ESXi's path. Removing the Dom0, growing the kernel, and moving to limited, enterprise only, hardware support.
I'm pretty sure they don't have the resources to do that. Nor is there any need - Xen as a commercial offering isn't anything to write home about, and as opensource, there isn't much demand for a slim hypervisor-only OS without cluster-level management abilities. Citrix might do something like that for the same reasons ESXi is available for free - as a first dose to get people hooked, but I'm not sure they can or want to invest so much in such an offering.
They are at record support numbers now that Citrix has bowed out. Citrix was blocking that back when they were involved. Now that Citrix's sabotage of Xen is done, Xen is picking up again as people see their efforts bearing fruit.
Citrix wouldn't do that as they aren't associated with Xen. Citrix has no interest in it (and really never did.) They wanted the name to start their "brand legacy tech virtualization to confuse customers" project. Citrix doesn't do anything virtualization related anymore, just some lingering money grabs with their old XenServer, but that's long dead.
I think it is Xen's obvious future. Xen has a lot going for it, but they need to leapfrog others to be seriously relevant.
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@scottalanmiller I frankly doubt there is much of a chance for Xen making anything worthwhile these days. With containers taking over most workloads and things like firecracker popping up, even KVM is losing ground. Openstack, the main locomotive for KVM adoption, isn't the cool new cloud platform any longer, and even it is adopting k8s and containers under the hood.
I think virtualization will become a niche platform technology in a few years, and if MS keep at their current direction, we might even see a common platform, where MS Windows 25 and Linux have the same base kernel and can easily run in the same container. We'll see
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@dyasny said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
@scottalanmiller I frankly doubt there is much of a chance for Xen making anything worthwhile these days. With containers taking over most workloads and things like firecracker popping up, even KVM is losing ground. Openstack, the main locomotive for KVM adoption, isn't the cool new cloud platform any longer, and even it is adopting k8s and containers under the hood.
KVM's focus is definitely Windows workloads that are bloated and can't be made thinner like we see in the Linux world.
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@dyasny said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
I think virtualization will become a niche platform technology in a few years, and if MS keep at their current direction, we might even see a common platform, where MS Windows 25 and Linux have the same base kernel and can easily run in the same container. We'll see
I agree. Full virtualization and even the Windows kernel itself have seen their day. The future is lighter, faster, and more converged.
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For those not familiar with Firecracker, it's a container (Type C) virtualization technology focused on server-less computing like AWS Lambda. It is open source under Apache 2.0 and sponsored by Amazon.
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@scottalanmiller said in What would your recommendation be for a Type 1 Hypervisor - including backup and restoration options:
KVM's focus is definitely Windows workloads that are bloated and can't be made thinner like we see in the Linux world.
Not really, I see a lot of KVM on large public openstack deployments (think digitalocean or vultr or whatever) and also in private DCs. Been migrating customers from VMWare and Xen to KVM for years, probably tens of thousands of hosts, if not hundreds, with most of those workloads being Linux VMs. That is pretty much where containers are taking a bit out of all other hypervisors' pie, with workloads becoming shorter lived and more ad-hoc and micro-servicy, this tendency will only grow.
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@scottalanmiller its basically just a replacement for QEMU, still using the same KVM, but more lightweight and much faster. Less features of course. So you end up with a lightweight (compared to QEMU) emulation plus a KVM hypervisor.
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@dyasny said in 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:
KVM's focus is definitely Windows workloads that are bloated and can't be made thinner like we see in the Linux world.
Not really, I see a lot of KVM on large public openstack deployments (think digitalocean or vultr or whatever) and also in private DCs.
Most of those are Windows focused. If they didn't want to support Windows, they'd go to LXC. KVM is a lot of overhead that only makes sense when Windows is in their game plans, or potentially ISO support. Vultr and OpenStack are almost completely doing this because of their Windows options. IMHO
