From the VMware Field: Mike D's Virtualization Blog

Why Does Xen have a 64-bit Hypervisor

Scott Lowe asked a great question on his blog today - Why does XenSource tout having a 64-bit hypervisor? I mean really, what does it give them that VMware doesn't already have? More host memory support? No. VMware supports 256 GB and XenSource supports 128 GB. More guest memory? No. VMware supports 64 GB and XenSource supports 32 GB. More guest support? No. VMware supports more 64-bit guests than XenSource does. VMware was also the first virtualization vendor with 64-bit guest support. So what are the benefits of the 64-bit hypervisor that XenSource is touting.

I think Keith Adams from VMware told it best on why VMware doesn't need to go 64-bit in the hypervisor.

I’ve worked in VMware’s virtual machine monitor group since 2000. I’m part of the three-person team who initially brought up 64-bit VMs on AMD hardware before SVM in 2004, and I am the one person team who brought up 64-bit VMs on Intel hardware with VT in 2005.

Our “hypervisor,” the vmkernel, is indeed 32-bit in ESX 3i. However, we make a distinction between our “monitor” and our “hypervisor” that is unfamiliar to Xen folks. Our “monitor” runs at CPL-0 on the bare metal, but is instanced; there is one monitor per VM. The monitor is what actually emulates the CPU, constructs shadow pagetables, programs VT/SVM hardware if appropriate, etc.

Our monitor has been 64-bit (on capable hardware) since 2004. Since the CPU-facing part of the software is 64-bit, it greatly reduces the pressure on us to move the vmkernel to 64-bit. Our customers understand this. When Xen Source sales people try to sell Xen by saying “Xen == 64-bit == new hotness, VMware == 32-bit == old n’ busted”, our customers are right to make fun of them on their blogs, IMHO.

[From A Few Thoughts on Xen - blog.scottlowe.org - The weblog of an IT pro specializing in virtualization, storage, and servers]

So there you have it. Finally someone called XenSource out on more of their rhetoric. I'm sure I'll get a bunch of the XenSource fans flaming me on my blog too just like they did to Scott. That's fine. Just make sure you come with facts this time and not more rants.

DISCLAIMER: These thoughts are my own and are not reflective of my company or anyone or anything else on planet earth.

VMworld Europe 2008

VMworld Europe 2008 is right around the corner - next week! Exciting times. I'll be over there presenting session RW05 - Software Licensing Exposed on Wednesday and Thursday as well as session RW02 - Scaling Your Virtual Infrastructure on Wednesday. Schedule and descriptions available here. I hope to see you all over there!

Is VMware Killing the Storage Industry?

That seems to be the message still coming out of Virtual Iron. I thought Ed Walsh's conversation about this had died off a long time ago. Apparently I was mistaken since it came up at a customer again yesterday. Ed is the CEO and President of Virtual Iron. He gave a talk at Storage Decisions late last year that appeared on YouTube. He also recorded a rather humorous "cocktail hour" talk and posted it to YouTube as well. Both say basically the same thing - VMware is killing the storage industry. I really have a hard time believing that.

Citrix Acquires XenSource - Still Scratching My Head

As I get back to reading through my emails and blog posts after holiday and week long meetings I find myself scratching my head over Citrix's Q4 earnings call - especially as it relates to XenSource. For those not living under a rock Citrix bought a startup called XenSource in late 2007. XenSource is a good little company with a good initiative in the open source community. What amazed me is the price Citrix paid for it - $500 million. That's just crazy!

Migrating from Intel to AMD

I was at a customer this week that told me Microsoft could migrate live between AMD and Intel processors and asked why we (VMware) couldn't. I actually get this question a lot and so I'm providing some context to the answer here. Microsoft and XenSource and all of the other competitors out there that do some sort of "live" migration run into the exact same issues that we do. Here's what's happening. Basically you're running an OS on an Intel box and let's say the processor supports the SSE3 instruction set and your app happens to use that instruction. Now you migrate that to an AMD box that doesn't support SSE3 but the app is still using it and trying to use it. BAM! Your app and your OS will crash. This can happen with VMotion and Microsoft Quick Migration. Actually anyone that does live migration will get impacted by this. There are several "user mode" instructions like this that we can't mask out at the virtualization layer.

Where's the blog, man?

I've gotten a lot of emails from people lately asking where the new entries are. First, I've got to say wow! I didn't know you all actually read this stuff. I guess it's of value hearing from me so I'll try to pick up to pick up the pace. Second, I'll say it's going to be hard to pick up the pace too much. I've been going to see too many customers and taking too much vacation. Well, I guess there's no such thing as too much of either of those.

So here's my promise - at least one post a week. Tonight my wife's working late so I'll get another "real" post out before heading to bed. Thanks for all of the support. More to come....