From the VMware Field: Mike D's Virtualization Blog

The Whoas of I/O in Hyper-V

Coming from one of my favorite blogs out there is a little blurb on Hyper-V's I/O performance problems. It turns out that the only way to boot a VM is with an emulated IDE device. What's the problem with that? Well, according to Anthony F. Voellm, Principal Software Development Lead of Hyper-V at Microsoft, this directly impacts I/O performance because of the way the device works.

The IDE controller implements a well-known IDE controller and this means there is extra processing before the I/O is sent to the disk. This processing occurs in vmwp.exe (a user mode process that exists for each started VM. More on this in a later post). Once the IDE emulation is complete the I/O is sent into the Root Partition’s I/O Stack. I/O completion requires a trip back to vmwp.exe.

The SCSI controller is not emulated. The SCSI controller uses VMBUS (Virtual Machine BUS. More on this in a later post). The I/O's pass from the Child (aka Guest) Partition to the root over VMBUS and enter the I/O stack. You can already see one less process/machine context switch is required because vmwp.exe does not get invoked. Once and I/O completes its completion is sent over VMBUS.

There is a lot more to how both the IDE and SCSI controllers work however the descriptions below should help you to understand why SCSI controllers are the right choice for the best performance.

[From ALL TOPICS PERFORMANCE : Hyper-V: How to get the most from your virtualized disk performance]

VMware Patch Tuesday

Recently there was a well researched and accurate blog on the increase in patches coming out for VMware ESX Server. The post shows that VMware ESX had about 68 patches released this year. Why so many patches? Well, as Nand points out in the corporate VMware blog Vmware has moved to a more traditional release train where we issue patches individually instead of one lump sum. This is the same method used by most larger ISVs (software vendors). For example, you’ll occasionally get patch notifications from Microsoft with several security, functionality, and driver updates. These Microsoft events have become known as “Patch Tuesday” since they come out on the second Tuesday of each month. FYI...This is also known as “Black Tuesday” to many since no one likes to administer a bunch of patches.

Intro

Welcome to my Blog. I am new to blogging so bear with me. I created this blog to set out some truth in the world. I’m of the opinion that bad journalism and marketing in general will kill this world we live on. Perhaps I’m a little paranoid. I just see a ton of bloggers and even real journalists out there perfecting the art of “copy and paste”. Very little research and thought goes into a lot of the stuff you see on the web or in more traditional print. So here I am with my own little corner of the web and a chance to show off my lack of journalism skills.

This blog will be about a lot of things I see in my life. As a professional I work for a small company called VMware. You may have heard of our rather successful IPO. I’ll blog more about VMware later. In my personal life I’m married with two great dogs and a beautiful wife. I enjoy flying in my “free time” as well as snow skiing and life at the beach (although I live in Atlanta).

I’ll finish my thoughts with one statement. The opinions expressed on this blog are my own. They are not representative of the rest of my family (my wife often thinks differently than myself) or my company, VMware. If you decide to quote anything on this blog then do so in it’s entirety. Do not quote out of context or I will find and correct you.

One last warning....I speak my mind freely. I am not politically correct many of the times. If you disagree with something I say or find something that needs correction then please let me know. So, now that the intro is out of the way, let’s blog!