With OpenVZ you *can* run different Linux distros - RHEL/CentOS, Fedora Core, SuSE, Debian, Gentoo - to name a few. The only common thing between different virtual environments is the kernel - OpenVZ kernel.
It's the crappy freeware version intended to sell the upscale enterprise version.
First of all, *please* do not call it crappy -- that way you show your disrespect to OpenVZ developers -- and those guys should be much respected for the efforts they put into OpenVZ and generally the Linux kernel.
To the point -- OpenVZ is very stable and solid piece of software made by the brilliant team of kernel hackers. Whether you like the software or not, have a respect to the people who developed it (unless you are at least as brilliant as they are).
What makes this entry-version freeware so important?
It is what that makes people use Virtuozzo (or OpenVZ) and not Linux-VServer (or FreeVPS, or Xen, or VMware) for their purposes. Compare these products for yourself and find out.
Indeed, this is not entry level software, but a product based on years and years of development and experience. Virtuozzo is developed since circa 1999.
Most end-users won't care about this technology. <...>no more dual booting<...>
To my mind, let the "no more dual-booting" feature better comes from the things such as OpenOffice.
Most end-users will care about this technology because it makes things more secure. I have been to Intel Developers Forum recently, and they showed an example usage case for VT technology -- several instances of Winblows running in parallel -- one for games, one for Internet surfing, one for online-banking. And they told that every single user want this. Certainly it was a demo not a real product yet.
While I was seeing that presentation I though that Virtuozzo/OpenVZ is doing that for years - separate applications from each other. And this is indeed what every user wants - Intel is right - because it strengthens your security.
If XenFS is finished, then OpenVZ will provide a lot less isolation and a lot less resource sharing than Xen...
This is not just XenFS. The good thing about single kernel approach is there is a single place from which you control all the hardware resources. With Xen, it is hard (almost impossible) to change the amount of memory given to the guest, without restarting it. More to say, _all_ the memory you allocate for the Xen instance will be taken once you start it, whether it is actually used or not. So, you (1) waste memory, (2) can not reallocate it dynamically. This leads to worse scalability, i.e. you can not run as many Xen instances as you would do with OpenVZ.
And yes indeed, with OpenVZ you have both limits and guarantees for the resources such as memory. So, an OpenVZ instance (a VPS, a guest) is guaranteed (unless you overcommit the resources) to have not less than X megabytes of RAM, and is limited to Y megabytes of RAM. Because of that, you can have more instances running -- tests show that about 100 VPS can run happilly (with no to little swapping) on a box having 1GB RAM.
There are three different types of virtualization, they are outlined in this short article.
In short, OpenVZ uses the single-kernel virtualization approach, which differs from either VMware or Xen: instead of trying to emulate something, kernel is modified to support multiple isolated environments, so each such environment looks-and-feels like a separate server. Good things about it is (1) best possible performance (no to little performance overhead due) and (2) hardware resources (CPU, RAM etc.) are controlled from within a single kernel, so resources are used most effectively.
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With OpenVZ you *can* run different Linux distros - RHEL/CentOS, Fedora Core, SuSE, Debian, Gentoo - to name a few. The only common thing between different virtual environments is the kernel - OpenVZ kernel.
So what's so great about OpenVZ? What does it do that Xen doesn't already or won't be able to do soon?
A lot of things actually, please consider a just a few:
We can elaborate on this further.
It's the crappy freeware version intended to sell the upscale enterprise version.
First of all, *please* do not call it crappy -- that way you show your disrespect to OpenVZ developers -- and those guys should be much respected for the efforts they put into OpenVZ and generally the Linux kernel.
To the point -- OpenVZ is very stable and solid piece of software made by the brilliant team of kernel hackers. Whether you like the software or not, have a respect to the people who developed it (unless you are at least as brilliant as they are).
What makes this entry-version freeware so important?
It is what that makes people use Virtuozzo (or OpenVZ) and not Linux-VServer (or FreeVPS, or Xen, or VMware) for their purposes. Compare these products for yourself and find out.
Indeed, this is not entry level software, but a product based on years and years of development and experience. Virtuozzo is developed since circa 1999.
Most end-users won't care about this technology. <...>no more dual booting<...>
To my mind, let the "no more dual-booting" feature better comes from the things such as OpenOffice.
Most end-users will care about this technology because it makes things more secure. I have been to Intel Developers Forum recently, and they showed an example usage case for VT technology -- several instances of Winblows running in parallel -- one for games, one for Internet surfing, one for online-banking. And they told that every single user want this. Certainly it was a demo not a real product yet.
While I was seeing that presentation I though that Virtuozzo/OpenVZ is doing that for years - separate applications from each other. And this is indeed what every user wants - Intel is right - because it strengthens your security.
If XenFS is finished, then OpenVZ will provide a lot less isolation and a lot less resource sharing than Xen...
This is not just XenFS. The good thing about single kernel approach is there is a single place from which you control all the hardware resources. With Xen, it is hard (almost impossible) to change the amount of memory given to the guest, without restarting it. More to say, _all_ the memory you allocate for the Xen instance will be taken once you start it, whether it is actually used or not. So, you (1) waste memory, (2) can not reallocate it dynamically. This leads to worse scalability, i.e. you can not run as many Xen instances as you would do with OpenVZ.
And yes indeed, with OpenVZ you have both limits and guarantees for the resources such as memory. So, an OpenVZ instance (a VPS, a guest) is guaranteed (unless you overcommit the resources) to have not less than X megabytes of RAM, and is limited to Y megabytes of RAM. Because of that, you can have more instances running -- tests show that about 100 VPS can run happilly (with no to little swapping) on a box having 1GB RAM.
In short, OpenVZ uses the single-kernel virtualization approach, which differs from either VMware or Xen: instead of trying to emulate something, kernel is modified to support multiple isolated environments, so each such environment looks-and-feels like a separate server. Good things about it is (1) best possible performance (no to little performance overhead due) and (2) hardware resources (CPU, RAM etc.) are controlled from within a single kernel, so resources are used most effectively.