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Corrections to ZDNet blog ‘Microsoft’s Hyper-V puts VMware and Linux on Notice’

ZDNet posted a blog reviewing Microsoft Hyper-V beta “Review: Microsoft’s Hyper-V puts VMWare and Linux on notice” (February 14, 2008). The posting had some factual errors and other claims about VMware ESX Server – see below for a summary. The author of the blog has acknowledged the errors in the comments section of the blog but since most readers won’t read through all the comments, here is a summary of the correct statements about VMware ESX Server as well as counterpoints to various claims.

Claim: VMware ESX Server does not support SATA disks.

"… SATA disk drives, which are now commonplace on commodity x86 server machines, are not currently supported in VMWare ESX 3."

Correction: VMware ESX Server 3.5 supports SATA disks. The author has acknowledged this in the comments section.

Claim: VMware ESX Server always requires VMFS and a dedicated SAN-based LUN to store virtual machine images.

“ESX Server also requires a special networked clustered file system known as VMFS to store the virtual machine images, and you have to dedicate a SAN-based LUN to it.”

Correction: ESX Server provides four options for VM storage: 1) Fiber channel (FC) attached, 2) iSCSI attached, 3) NFS, and 4) local storage. Only the FC and iSCSI options require a SAN-based LUN. Also, the NFS option does not use VMFS. Again, the author has acknowledged this error in the comments section. Note that Citrix XenServer and Microsoft Hyper-V also require shared storage to perform VM migration and other high availability functions.

Claim: VMware is a closed system. Therefore, VMware development goes at a much slower pace. VMware’s lack of SATA disk support is an example of this slower pace.

“VMWare keeps its ESX hypervisor source code very close to the vest, so development goes at a much slower pace – SATA disk drives, which are now commonplace on commodity x86 server machines, are not currently supported in VMWare ESX 3.”

Counterpoint: VMware’s purported lack of SATA disk support has already been refuted (see above). In addition, VMware has delivered more industry-breaking innovations around x86 virtualization compared to anyone else. As examples, VMware was the first to deliver virtual SMP, live migration (VMotion), centralized VM management (VC), dynamic load balancing (DRS), automatic VM restart after host failure (HA), next-generation thin embedded hypervisor (ESX Server 3i with a 32MB disk footprint), and Storage VMotion. The majority of other vendors still have not delivered these capabilities. VMware has also provided ESX Server source code to partners as part of the VMware Community Source Program. One good example of the output from the Community Source Program is the Mellanox Infiniband support.

Claim: VMware ESX Server’s hardware compatibility list (HCL) severely limits a customer’s hardware choices while Microsoft and Xen do not have this issue.

"However, [ESX Server] has a much tighter environment as to what kind of hardware it can run on – the hypervisor has a limited device driver compatibility list…"

Counterpoint: Both Microsoft Hyper-V beta and Xen-based products (ex. Citrix XenServer, Virtual Iron) have HCLs as well. Click here to see Microsoft’s list of hardware platforms “suitable” for Hyper-V beta. Click here to see Citrix XenServer’s HCL. Click here to see Virtual Iron’s HCL. The Microsoft, XenServer, and Virtual Iron HCLs are actually more limited than VMware’s HCL. For instance, Microsoft has directly tested Hyper-V beta on 8 servers (TBD what the hardware requirements will be for Hyper-V GA). Citrix has directly tested 45 servers. Virtual Iron has directly certified 29 servers (for version 4). In contrast, VMware has over 400 servers on the ESX Server 3.0.2 HCL. Click here to see VMware’s HCL.

Claim: VMware ESX Server is “pure software based virtualization”

"VMWare’s ESX differs from Hyper-V and Xen in that it currently uses pure software based virtualization…”

Counterpoint: This statement can potentially mislead readers to think that ESX Server is based on software emulation technology. This conclusion would be false. For the bulk of x86 CPU instructions, ESX Server does direct execution on the physical CPU. Readers may also interpret this statement to say that VMware is somehow philosophically opposed to using CPU hardware-assist. Again, this would be a false conclusion. VMware takes a pragmatic approach and uses whichever technology delivers the best performance. Currently VMware binary translation has advantages over today’s generation of CPU hardware-assist. Click here to read a VMware whitepaper on this topic. In regards to the future, VMware is already working closely with Intel and AMD on their next-generation of CPU hardware-assist technology.

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