Letters - 27 Aug 2008

A Reader Responds: Hyper-V vs. VMware ESX Server
After reading Michael Otey’s “Virtualization Shootout, Part 1” (June 2008, InstantDoc ID 98879), I’ve grown more interested in Hyper-V. However, I’m still unclear about a couple things:

1. Cost—When you compared the cost of VMware ESX Server with that of Hyper-V, did you include the cost of Microsoft System Center Virtual Machine Manager (SCVMM)? As the article mentions, you need SCVMM to perform quick migrations. I believe a Virtual- Center for VMware Server license is included in the VMware Infrastructure 3 (VI3) Foundation bundle.

2. Migrations/Vmotion—For enterprise systems, VMware’s Vmotion technology is a must-have. Obviously, Microsoft’s quick migration isn’t live. But what exactly does “quick migration” mean to an administrator or end user?

3. Drivers—The article mentions that ESX Server’s drivers are in the hypervisor and that Hyper-V’s drivers are in the guest OS. What are the repercussions for VM migrations? In VI3, because the drivers are in the hypervisor, the guest OS receives generic drivers that are “portable” across the infrastructure. Typically, the only concern with migrating VMs in VI3 is ensuring that your CPUs contain the same feature set. However, even if the CPUs are different and support different features, the VMs can still be migrated cold and brought up on the dissimilar hardware with no problems.

Thank you for your help with these questions. I look forward to further articles about Hyper-V in the coming months.

—Brent McCraney

The cost comparison doesn’t include the cost of SCVMM, which is required for quick migrations. Likewise, it doesn’t include the cost of VirtualCenter for VMware Server on the ESX Server side. VirtualCenter is included in the high-end editions of the VI management platform. However, it isn’t included in the low-end VI3 Foundation edition, which we used in our comparison.

VMotion is certainly useful for unplanned downtimes. But it isn’t necessary for most VM implementations. VMotion permits the movement of VMs between hosts without shutting down the VM. You’ll experience a delay in responsiveness while the VM movement takes place. But when the process is done, the VM is in the same state that it was prior to the move. By contrast, Microsoft’s Quick Migration saves the state of a VM before the move, making the VM temporarily unavailable. Then, the system moves the VM and restores the state. A brief interruption of service occurs during the move. But the process is far quicker than shutting down and restarting the VM.

The location of the drivers in the parent partition doesn’t affect the ability to migrate VMs between Hyper-V servers. Hyper-V VMs are completely portable, just as ESX Server VMs are.

—Michael Otey

Setting Up a Cisco Router
I enjoyed Michael Dragone’s article, “9 Steps to Setting Up a Cisco Router” (June 2008, InstantDoc ID 98740). I have a quick question about Listing 1’s extended access list 101. I don’t think you need the first line: permit udp any eq bootps any eq bootpc. I think the third line—permit udp any any—is a superset of the first line and more than covers for it.

—Dimitrios Kalemis

You’re correct. The third line of access list 101 would account for line 1 and, in fact, make it redundant. Most environments probably wouldn’t need it; I have it in mine only so that I can receive a public routable IP address from my ISP. In addition, I have some Deny statements in my access lists that make it a requirement to have line 1 present. I apologize for any confusion the code caused.

—Michael Dragone

Microsoft Responds: Hyper-V vs. VMware ESX Server
According to the development schedule specified in “Virtualization Shootout, Part 2” (July 2008, InstantDoc ID 99248), Microsoft’s Hyper-V was tested using prereleased beta code. The performance data in the review may not represent an apples-to-apples comparison because all the performance optimization occurs at the very end of the development cycle.

Microsoft customers and partners are seeing great cost savings and performance results within their datacenters. Most recently, QLogic published a benchmark for I/O throughput for storage devices going through Windows Server 2008 Hyper-V. At 180,000 I/Os per second on a system running Hyper-V, virtual machine connections are just 10 percent shy of native performance. This benchmark demonstrates Hyper-V’s ability to bring the advantages of virtualization to the most demanding datacenter. For more information about installing and testing Hyper-V, please check out the tuning guide at www.microsoft.com/whdc/system/sysperf/Perf_tun_srv.mspx.


We’re performing another round of tests with production code and will publish the results later this year.

—Amy Eisenberg

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