It’s been gratifying to see lots of folks finding my site a couple of months after my first post, reading the article “KVM is Linux, Xen is Not“, and retweeting it to a broader audience. I seem to have hit a nerve, and I hope I have provided some value in helping folks understand the differences between KVM and Xen.
If you’ve read in the last couple of weeks, you probably noticed that posting has attracted some less than positive comments from Xen adherents.
All cards on the table: I am a KVM adherent. I work for Red Hat, and I work on a KVM-based product. Moreover, I personally believe that KVM is the best technology going forward for open source virtualization.
My goal in the post was to point out the architectural differences between Xen and KVM, before and after the inclusion of some Xen code beginning with Linux 3.0. And yes, to poke some fun at Citrix and Oracle.
Based on the recent comments I’ve gotten, I thought it was worth writing a short post before going on to other topics.
I was tempted to do some editing to the original post (a footnote here, a qualification there), but aside from fixing a couple of incorrect links, I decided to let it stand as originally written and posted for better or worse.
I do apologize for initially pointing to the incorrect article as the attribution link for Simon Crosby’s quote. I have made that correction in the post.
But unless there are technical inaccuracies, I am not making any further edits. You the reader can decide if I was fair, pushing things to make a point, or way off base and need to apologize for muckraking.
Let’s step back in time a bit…
Now, the post is a bit out of its historical context. After all I wrote most of it in July of 2011 for a different forum to address a real issue–the confusion about what Xen being “accepted” into Linux actually means.
Confusion still reigns
Almost a year later, people still ask what that announcement from Oracle and Citrix means. And still the overwhelming impression that people come away with from reading the coverage and talking to sales people is that Xen is now integrated into Linux, and that KVM’s advantages in that regard are moot.
Addressing that confusion was the ultimate intent of the post.
Was it a bit cheeky to call out the Oracle and Citrix at the top of the article? Sure. Guilty as charged. It helped get the post out to a broader audience than I expected for what at its heart is a relatively dry but important architectural distinction.
Is there anything technically inaccurate in the post? I haven’t heard of anything yet, but I commit to immediately correct any technical inaccuracies.
Did I not give the people behind the posts the benefit of the doubt? Maybe. I admit I was fixated on the inaccuracies and FUD circulating at the time.
I will say this: if you understand enough about the architecture of Xen, of KVM, and the process of including code in the Linux kernel, then reading in full the cited articles will give you an accurate account of what the Xen announcement means for Xen and for KVM.
If however you don’t know hypervisor architectures that well, or you only read the press and second hand accounts, or what a sales person told you, or the headlines and soundbites, then you probably got the wrong impression. This article was written for you.
I’m moving on to other topics. Feel free to comment.