When faced with a tirade of client consultations and disaster recovery proposals/assessments, you can’t help but be inundated with opportunities to showcase the benefits of server virtualization and more specifically VMware’s Site Recovery Manager. It’s a given that if an environment has a significant amount of applications running on X86 platforms, then virtualization is the way to go not just for all the consolidation and TCO savings but for the ease in which high availability, redundancy and business continuity can be deployed. Add to that the benefit of a virtualized disaster recovery solution that can easily be tested, failed over or failed back. With what was once a complex procedure, testing can now be done via a simple GUI based recovery plan. Thus one should consequently see the eradication of trepidation that often existed in testing out how full proof an existent DR procedure actually was. Long gone should be the days of the archaic approach of the 1000 page Doomsday Book-like disaster recovery plans which the network, server and storage guys had to rummage through during a recovery situation, often becoming a disaster within itself. Hence then there really is little argument to not go with a virtualized DR site and more specifically VMware’s Site Recovery Manager, but not so it seems if you’ve been cornered and inculcated by the Microsoft Hyper V Sales team.
Before I embark further, let’s be clear that I am not an employee or sales guy for VMware - I’m just a techie at heart who loves to showcase great technology. Furthermore let it go on record that I’ve never really had a bone of contention with Microsoft before – their Office products are great, Exchange still looks fab and I still run Windows on my laptop (albeit on VMware Fusion). I even didn’t take that much offense when I recently purchased Windows 7 only to realize that it was just a well marketed patch for the heir to the disastrous Windows ME throne i.e. Windows Vista. I also took it with a pinch of salt that Microsoft were falsely telling customers that Exchange would run better on local disks as opposed to the SAN in an attempt to safeguard themselves from the ongoing threat of Google Apps (a point well exposed and iterated on David Vellante’s Wikibon article, “Why Microsoft has it’s head up it’s DAS”). Additionally my purchase of Office 2010 in which I struggled to fathom the significant difference between Office 2007, still didn’t irk me that much. What has turned out to be the straw that broke the camel’s back though is the constant claims Microsoft are making that Hyper-V is somehow an equally good substitute to VMware and consequently pushing customers to avoid a Disaster Recovery Plan that includes Site Recovery Manager. So what exactly are the main differences between the two hypervisors and why is it that I so audaciously refuse to even consider Hyper-V as an alternative to VSphere 4?
Firstly one of the contentions often faced with virtualizing is the notion that some applications don’t perform well if at all when on a virtualized platform. This is true when put in the context of Hyper V, which currently limits the number of vCPUs to only 4. That’s pretty much a no go for CPU thirsty applications leading to an erroneous idea that a large set of applications should be excluded from virtualization. This is not the case when put in the VSphere 4 context where guests can have up to 8 cores of vCPUs. In an industry which is following a trend of CPUs scaling up by adding cores instead of increasing clock rates, the future of high-end x86 servers provides a vast potential for just about any CPU hungry application to run on a virtualized platform – something VSphere 4 is already taking the lead in.
Then there’s the management infrastructure in which Hyper V uses software named Systems Center (SC) and more specifically the Systems Center Virtual Machine Manager (SCVMM), whereas the VSphere4 equivalent is named vCenter Server. With Hyper-V being part of a complete Microsoft virtualization solution, System Center is generally used to manage Windows Server deployments. The System Center Virtual Machine Manager on the other hand not only manages Hyper-V-hosted guests but also Virtual Server, VMware Server and VMware ESX and GSX guests. Ironically this can then also be extended to managing vMotion operations between ESX hosts, (perhaps an inadvertent admission from Microsoft that vMotion wipes the floor off their equivalent Live Migration). Compared to vCenter Server which can either be a physical or virtual machine this comes across as somewhat paltry when VSphere 4 now offers the ability to allow multiple vCenter servers to be linked together and controlled from a single console, enabling a consolidated management of thousands of Virtual Machines and several Datacenters. Add to this the functionality that vCenter Server provides a search-based navigation tool that enables the finding of virtual machines, physical hosts and other inventory objects based on a user defined criteria and you have the ability to quickly find unused virtual machines or resources in the largest of environments all through a single management pane.
Taking the linked management capabilities of vCenter further, VSphere 4 also offers what they term the vNetwork Distributed Switch. Previously for an ESX server a virtual network switch was provisioned and managed and configured. With the vNetwork Distributed Switch, virtual switches can now span multiple ESX servers while also allowing the integration of third-party distributed switches. For example the Cisco Nexus 1000v is the gateway for the network gurus to enter the world of server virtualization and take the reins of the virtual network which were previously being run by VM system admins. Put this in the context of multiple vCenter Servers in the new linked mode and end users have the capability to not only manage numerous virtual machines but also the virtual network switches. In an Enterprise environment where there are hundreds of servers and thousands of virtual machines, what previously would have been a per-ESX switch configuration change can now be done centrally and in one go with the vNetwork Distributed Switch. Hyper V as of yet has no equivalent.
That broad approach has also pushed VMware to not only incorporate the network guys into their world, but also the security and backup gurus. With VSphere 4’s VMSafe, VMware have now enabled the use of 3rd party security products within their Virtual Machines. An avenue for the security guys to at last enter the virtual matrix they previously had little or no input in. Then there’s the doorway that VSphere 4 has opened for backup gurus such as Veeam to plug into virtual machines and take advantage of the latest developments such as Change Block Tracking and vStorage APIs bringing customers a more sophisticated and sound approach to VM backups. Hyper V still has no VMsafe equivalent and certainly no Change Block Tracking.
Furthermore as Microsoft flaunt Hyper V’s latest developments, scrutiny shows that they are merely features that have been available on VMware for several years and even then still don’t measure up in terms of performance. Point in case being Hyper V’s rather ironically titled ’Quick Motion’. For high availability and unplanned downtime protection Hyper-V clusters have a functionality that restarts Virtual Machines on other cluster nodes if a node fails. With ‘Quick Motion’ a Virtual Machine is then moved between cluster hosts. Where it fails though is in its inability to do the action instantly as is the case with VMware’s vMotion and HA features. This hardly exudes confidence in Hyper V when a potential move that can take several seconds leaves you exposed to the risk of a network connection failure which consequently results in further unplanned downtime. Subsequently Quick Motion’s inability to seamlessly move Virtual Machines across physical platforms results in downtime requirements for any potential server maintenance. This is certainly not the case with VMware and vMotion wherein server maintenance requiring downtime is a thing of the past.
Moreover so seamless is the vMotion process that the end user has no idea that his virtual machine has just crossed physical platforms while they were inputting new data. This leads us to Hyper V’s reaction and improved offering now termed Live Migration which Microsoft claim is now on a par with vMotion. Upon further inspection this still isn’t the case as the amount of vMotion operations that can be simultaneously done between physical servers is still far more limited with Hyper V. Additionally while Hyper V claims to be gaining ground, VMware in return have shot even further ahead with VSphere4’s Storage vMotion capabilities which allows ‘on the fly’ relocation of virtual disks between the storage resources within their given cluster. So as VMware advances and fine tunes its features such as Distributed Resource Scheduler, Distributed Power Management (DPM), Thin Provisioning, High Availability (HA) etc., Hyper V is only just announcing similar functions.
Another issue with Hyper-V is that it’s simply an add-on of Windows Server which relies on a Windows 2008 parent partition i.e. it’s not a bare metal hypervisor as virtual machines have to run on the physical system’s operating system, (something akin to VMware’s Workstation). Despite Microsoft’s claims that the device drivers have low latency access to the hardware, thus providing a hypervisor-like layer that runs alongside the full Windows Server software, in practical terms those that have deployed both Hyper V and VMware can testify the performance stats are still not comparable. One of the reasons for this is that VMware have optimized their drivers with the hardware vendors themselves unlike Hyper V which sadly is stuck in the ‘Windows’ world.
This leads to my next point that with VSphere 4 there is no reliance on a general operating system and the various operating systems that are now supported by VMware continues to grow. Microsoft on the other hand, being the potential sinking ship that she is in the Enterprise Datacenter have tried to counter this advantage with marketing Hyper V as being able to run on a larger variety of hardware configurations. One snag they don’t talk about so much is that it has to be a hardware configuration that is designed to support Windows. Ironic when one of the great things about virtualization is that Virtual Machines with just about any operating system can now be run together on the same physical server, sharing pools or resources – not so for Microsoft and Hyper V who desperately try to corner customers to remain on a made-for-PC operating system that somehow got drafted into datacenters. Question now is how many more inevitable reboots will it take on a Windows Enterprise Server before IT managers say enough is enough?
Then there are some of the new features that were introduced in VSphere 4 which still have failed to take similar shape in the Hyper V realm. For example VMDirectPath I/O which allows device drivers in virtual machines to bypass the virtualization layer and access the physical resources directly – a great feature for workloads that need constant and frequent access to I/O devices. There’s also the Hot-Add features wherein a virtual machine running Windows 2000 or above can have its network cards, SCSI adaptors, sound cards, CD-ROMs added or removed while still powered on. They even go further by letting your Win 2003 or above VM hot add memory or CPU and even extend your VMDK files – all while the machine is still running. There’s still nothing ‘hot’ to add from the Hyper V front.
Also instead of the headache inducing complexities that come with Microsoft’s Cluster Service, VSphere 4 comes with Fault tolerance – a far easier alternative for mission critical applications that can’t tolerate downtime or data loss. By simply creating a duplicate virtual machine on a separate physical host and via vLockstep technology to ensure consistency of data, VSphere 4 offers a long awaited and straightforward alternative to complex clustering that further enhances the benefits of virtualization. No surprise then that currently the Microsoft Hyper V sales guys tend to belittle it as no great advantage.
Another VSphere 4 feature which also holds great benefits and is non-existent in Hyper V is that of Memory overcommitment. This feature allows the allocation of more RAM to virtual machines than is physically available on the physical host. Via techniques such as Transparent page sharing, virtual machines can share their common code thus leading to significant savings in the all too common situation of having to add more memory to an existent server which equates to more than the cost price of the server.
So while Hyper V has also recently caught up with a Site Recovery Manager equivalent with the Citrix Essentials for Hyper V package, it’s still doing just that i.e. playing catch up. One of the main arguments for Hyper V is that it’s free or nearly free but again that’s the marketing jargon that fails to elaborate that you have to buy a license for a Windows Server first and hence help maintain the dwindling lifespan of Microsoft within the Datacenter. Another selling point that Hyper V had was that they were better aimed for small to medium sized businesses due to their cheaper cost….the recent announcement of VSphere 4.1 may now also put bed to that claim. So like all great empires, collapses are imminent and while I don’t believe Microsoft are going to the I.T. Black Hole, they certainly don’t look like catching up with VMware in the ever emerging and growing market of virtualization.