Talk:Xen/Archive 2006

Comparison to UserModeLinux?
How do they stack up, what's the main difference? --Anon.


 * UML =Linux only, less efficient, but does not need kernel modified (the host kernel might need to be, I'm not sure, but I'm fairly sure the guest kernels can run straight), more tested etc. --Maru 12:42, 24 August 2005 (UTC)


 * UML certainly does require modified guest kernels although uml is now part of the official kernel tree so its just a compile option now.
 * The host kernel doesn't need to be modifed for uml but uml can run a lot more efficiantly if it is. --Plugwash 13:02, 24 August 2005 (UTC)


 * /shrugs. Good thing I don't edit the UML article then. --Maru 13:14, 24 August 2005 (UTC)


 * We definitely should have UML mentioned in there. Mark Williamson 01:41, 31 August 2005 (UTC)

where did you heard that uml was less eficient... look atentively at xen benchmark against uml...uml is a 2.4 kernel!!!...and uml patch has been integrated and avaliable by default inside the  2.6 branch since 2.6.??...so we need to test them...by the way i use gentoo and linux kernel ported to xen is hard maskered(that means that it has a problem...such as security or other...i should ask them if i can use it safely,because some of their masked package can be used safely if you know the problem...for example a security bug in a game(unreal tournament) used as a game server=>if you use it only as client...you don't have problems)


 * It's well known to be less efficient, although that is only important if efficiency is your concern. With UML, the guest's instructions are being executed in terms of a user space program which means context switching. You need at least two fully-fledged operating systems. With Xen, you have the Xen OS which is pretty small, plus your guests. -- 82.39.205.158 23:58, 29 July 2006 (UTC)

Link to xen-forums
There are too many links in the External Links section. To start with, I'm removing the xen-forums link as it is not very popular (there are only a handful of posts). Anthony Liguori --70.116.9.243 06:21, 31 May 2006 (UTC)

Popularity contest
With an annual VMM product revenue in excess of US$600 million (as of Q2 2006), VMware is by far the most popular VMM for Windows virtualization.

??? Sales =! Popularity, especially when people don't pay for most of the products listed. Bruce 04:15, 18 August 2006 (UTC)

This page needs serious work
A good portion of the info on this page is factually incorrect. I've gone through and marked the most objectional paragraphs as unreferenced but in relately, as a Xen developer, I know the information is wrong. Among the biggest problems are the reference to Xen supporting all x86 Operating Systems (that's based on a quote from Simon Crosby about Xen supporting all *major* x86 Operating Systems--well, he's wrong but leaving out that major qualifier makes a big difference). The information about Microsoft's support for Xen is also wrong. Viridian is the codename for their hypervisor--not some sort of Xen implementation. Microsoft merely licensed the Viridian guest API to XenSource. XenSource is building a shim to allow Xen guests to run under Viridian. Finally, the performance numbers are, at best, uncited. In reality, software bridging alone will cause a 10% performance impact on any sort of network-heavy workload. The true numbers are certainly much higher. Xen is still considerably faster than something like VMware...

I'm going to sit on this for a little bit with the hope that someone proves me wrong and references all of this. Otherwise, I think it's appropriate to rewrite most of the content of this page. -- AnthonyLiguori --70.112.17.156 15:06, 19 September 2006 (UTC)

I've started cleaning up this page. Please be care when adding new content. Wikipedia has policies on external linking that should be consulted before adding. I also removed the comparision section as it's duplicated elsewhere in wikipedia. I've removed any reference to Microsoft shipping a Xen port. They aren't. I've clarified the relationship between XenSource and Microsoft. I've also removed references to an, at worse, 8% performance impact. That's just not true. Again, please reference performance numbers in the future. -- AnthonyLiguori --70.112.17.156 05:14, 21 September 2006 (UTC)

Plan 9 and virtualisation
it seems that unix cope it's limitation with virtual machines...

plan 9(open-source and fsf aprooved) achive the same thing(jailying apps inside some resource) in a different way... see here mabe we can talk about theses limitations and tell that virtualisation is the most used solution but that others exist...


 * I think that discussion belongs on a more general 'virtualization technologies' page.--LukeCrawford 19:49, 13 September 2006‎ (UTC)

The comparison section is unnecessary
1. No actual comparisons are being made. This section only contains 1 or 2 sentence factoids about other VMM. For reference, a comparison is defined as: 1. The act of comparing or the process of being compared. 2. A statement or estimate of similarities and differences. Again, neither of these actions occur in the "comparison" section; what this section does is summarize other VMM's that are on the market.

2. Partly because of the lack of comparisons to Xen, this section does little to further the reader's understanding of Xen (which is the focus of the article). This section needs to be removed from the Xen article and given its own article-space, perhaps under the heading of "VMM synopsis" or some other appropriate title.

For reference, I direct you to the article on OpenVZ. This article has a brief paragraph comparing it to 2 other VMM's, and it makes real comparisons.

—Preceding unsigned comment added by 138.23.210.36 (talk) 22:02, 21 August 2006‎ (UTC)

Do not place external links to web consoles for Xen
Wikipedia has a strict external linking policy. See Also should only contain interwiki links. External links should only be for official sites or deeper information that wouldn't be appropriate for the article itself.

—Preceding unsigned comment added by 70.112.17.156 (talk) 04:27, 27 September 2006‎ (UTC)

Enlightenments
The main section says "ported", aka "enlightened". They really aren't the same thing. Enlightments are a term invented by Microsoft to describe their paravirtualization technique. Viridian actually relies on having full virtualization capabilities in the hardware and essentially always runs a guest in full virtual mode. However, to acheive performance similar to a true paravirtual hypervisor, they "enlighten" the Operating System such that things that would normally be a bottleneck under full virtualization (for instance, a mass update of a PTE), can be batched. This really isn't what Xen currently does.

—Preceding unsigned comment added by 70.112.17.156 (talk) 04:34, 27 September 2006‎ (UTC)