Quotes of the week [LWN.net]

Today's other accomplishment was spending long enough looking at Toshiba ACPI dumps to figure out how to enable hotkey reporting without needing to poll. Of course, I then found that the FreeBSD driver has done the same thing since 2004. Never mind.

-- Matthew Garrett

The real difference between KVM and Xen is that Xen is a separate Operating System dedicated to virtualization. In many ways, it's a fork of Linux since it uses quite a lot of Linux code.

The argument for Xen as a separate OS is no different than the argument for a dedicated Real Time Operating System, a dedicated OS for embedded systems, or a dedicated OS for a very large system.

Having the distros ship Xen was a really odd thing from a Linux perspective. It's as if Red Hat started shipping VXworks with a Linux emulation layer as Real Time Linux.

-- Anthony Liguori

You say, "You never know when your MB, CPU, PS" may bite the dust. Sure, but you also never know when your RAID controller will bite the dust and start writing data blocks whenever it's supposed to be reading from the RAID (yes, we had an Octel voice mailbox server fail in just that way at MIT once). And you never know when a hard drive will fail. So if you have those sorts of very high levels of reliability requirements, then you will probably be disappointed with any commodity hardware solution. I can direct you to an IBM salesperson who will be very happy to sell you an IBM mainframe, however.

-- Ted Ts'o

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Quotes of the week

Posted Mar 12, 2009 23:04 UTC (Thu) by MarkWilliamson (guest, #30166) [Link]

Painful as I sometimes find Xen, the hypervisor is much not so much a fork of Linux as it
once appeared.

It looked quite like a fork in the Xen 1.x days, since it also contained lots of Linux device
drivers, etc. It still pulls in a fair bit of Linux code for a) utility functions (spinlocks, generic
datastructures..) and b) low level hardware support. However, the rest of the code is often
extremely different from Linux since it uses different abstractions and interfaces - there's
enough core Xen-specific code added and core Linux code removed that it really looks like
a very different animal.

I think it would be better to question whether the combination of Xen + dom0 constitutes a
fork of Linux with some code moved about to funny places and some extra protection
domain crossings. I think that would be a highly valid question to ask, though as usual, it's
quite not that simple :-S

I'm skeptical whether (especially with improving hardware support for virtualisation) Xen's
approach is going to (continue to?) hold much merit over its competitors. Equally, it seems
to be still making good progress in functionality and a lot of people use it. It'd be nice to
see it finally merged in kernel if it can be done tastefully - the out-of-tree code is causing
people pain at the moment, which is always the problem with such things!

Disclaimer: Have worked on Xen, still do research related to it.