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» VIEW ALL POSTS Apr 3 2008   7:33AM GMT

The pros and cons of Virtuozzo: A user review



Posted by: SAS70ExPERT
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Atlanta-based virtualization pro Mark Dean shares his thoughts in a guest blog for SearchServerVirtualization.com

One of the more popular products in the growing virtualization market is Parallels Virtuozzo Containers. Virtuozzo Containers provide a stable, high performance virtualization platform. However, this same technology also has some drawbacks in restricting the operating systems that can be used for both hosts and VMs.

I deployed Virtuozzo for a customer that wanted to leverage virtualization but was uneasy about the performance of their database server. I suggested Virtuozzo since it straddles the physical-virtual line with OS containers, it is similar to the technology that Sun Solaris uses.

The strengths of Virtuozzo Containers are really in that blurred line between the physical and virtual platforms. Instead of a hypervisor between the OS and the hardware, Virtuozzo Containers virtualize the OS by sharing OS code, files, memory and cache from the root OS, which is called the Hardware Node (and is represented as Container ID 0) in Virtuozzo terms. This means that the VMs are using the hardware directly rather than having calls to the hardware trapped by a hypervisor and then executed which translates into better performance for I/O workloads. This increase in performance is one of the main reasons companies will deploy Virtuozzo. High I/O workloads such as heavy transaction based databases benefit from the shared code nature of the containers.

But as hardware advances with the option of CPU hardware assistance from the CPU manufacturers (AMD-V and Intel-VT), I see Virtuozzo’s technology becoming irrelevant. Since I can now run unmodified VMs using Xen or KVM on Linux and no longer have the (over-exaggerated) performance hit of the binary translation hypervisor (as in ESX), why go with a limiting technology?

Virtuozzo imposes some limitations on what you can run in your farm. Since the VMs are basically sharing code form the root Container OS, you can only run that type of VM on the host. Virtuozzo Containers currently only supports Windows 2003 Server and main Linux distributions. You cannot run Solaris, BSD or NetWare. Now, for some IT shops that may not be a problem but just about all the places I’ve seen, there is a mix of Unix, Windows and for many government places, NetWare.

If a virtualization vendor does not enable live migration, host/VM isolation or embrace the concept of a farm, it is not good for production workloads. Virtuozzo does have some of them, but their isolation is not as good as I like to see. I find that right now only VMware VI3 ESX 3.5 Server has all those concepts down. Xen Enterprise, when coupled with CPU assisted virtualization is the best contender to challenge VMware’s space right now.

Mark Dean is a VMware Professional Partner and a Microsoft Certified Partner with certifications in VMware, Microsoft, Novell, Citrix, IBM and HP along with HP and IBM hardware. Dean has his own virtualization consulting company, VM Computing.

7  Comments on this Post

 
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  • SAS70ExPERT
    I didn't see much about the pros and cons of Virtuozzo in this entry -- one pro (supposedly better performance) and a lot cons with a recommendation to run VMWare (this from a VMWare Professional Partner). There are a lot more pros for Virtuozzo (higher density per server, no need to install O/S in each VM, ease of access to each container, easier to allocate / manage storage, consistency of images and patch deployment) -- that's why it's highly used in hosting environments which require consistency and high density. Cons are as Mark has stated (less isolation), but also include things like less compatibility for things that need certain libraries and memory access. Perhaps my expectations are a bit high for this, but I expected more than a review from someone who has appeared to have installed Virtuozzo only once and is a noted VMWare expert.
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  • SAS70ExPERT
    For the record, I have 2 customers who run Virtuozzo 3, each with 2 hosts; I implemented the technology at both sites and provided initial support. They have a large investment in another virtualization platform but both had misgivings about running large production databases in the virtual space and wanted better I/O performance. I keep up with Virtuozzo like I do with other platforms using real snapshots of production VMs on tier 1, late model servers and put all feature sets through their paces. I never rely on the “marketecture” of sales engineers or demos. I don't have a lot of customers who run Virtuozzo because that's not want most want. Why? Let's see if this tracks: You spend $3000.00 for a 2 CPU license for Virtuozzo and you can run exactly one version of Windows 2003. So gone are any ideas of doing a server consolidation where you start with legacy systems like NT 4 and Windows 2000. Then, if you are like most companies, you have some Linux and you will have to shell out another $3000.00 for a Linux license to run any Linux VMs. If you are a school district or most any other government entity, and I subcontract for a VAR with contracts for several, you will not be able to run your Novell products at all. You can't lump your hardware hosts together and create a cloud of CPU, RAM, disk, and network resources and move any x86 workload around as needed-even automatically. No, Virtuozzo is more like a vertical application. It has very specific uses in the virtualization world. Parallels says that they sacrificed compatibility for stability and I agree, it is a very stable implementation. But that's only good if the alternatives are not stable and that's certianly not the case. I only had so much space to write about it, but yes, you are right, you have to have the OS a certain way and Virtuozzo is very picky about what patches and SP level you are at just to install it. Now if this really were the best route to take for virtualization, then why is Parallels working on a Parallels Server version that will be more traditional in its approach? For several years now they've been touting how bad hypervisor based systems are and how good OS virtualization is, yet now they will have a product that is just that. I couldn't be happier because I'll start to resale both soon. Now as for hosting, especially dedicated virtual hosting, one reason why Virtuozzo is used more is for the simple reason that VMware will not allow you to run VMs and lease them out to a third party. If they ever change that, look out. As far as my partnerships, my opinion is not dictated on what partnerships I have and will be the same after I finish the partnership application to become a Parallels partner. -md
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  • SAS70ExPERT
    Mark, I dont want to get in a long debate on the benefits / drawbacks of the technology as I will let the market do that, however I just want to clarify a few points. "Parallels says that they sacrificed compatibility for stability and I agree, it is a very stable implementation." While we are stable as you have agreed, what we actually have stated is that we sacrificed compatibility for performance. We never claimed VMs were unstable, only that they have a large performance hit even with VT technology. "Virtuozzo is very picky about what patches and SP level you are at just to install it." Virtuozzo will support both SP1 and SP2 just fine, service packs are not an issue. Hotfixes however can sometimes be. Given thatw e take advantage of low level APIs and leverage functionality in MS DLLs it is important we can test our software against any changes that may have been introduced by MS. While in most cases there are no issues, in some cases it requires a small change in Virtuozzo before we can ensure compatibility. BTW, Other vendors may also benefit from such a model. "Now if this really were the best route to take for virtualization, then why is Parallels working on a Parallels Server version that will be more traditional in its approach?" We also do not state that one solution fits all. And finally VMware was not able to capitalize on the shared hosting market not because of licenses only (albeit their licensing was never geared for a service model), the main problem there was density. Without being able to achieve a certain density on a given hardware it is impossible for a hosting company to offer a virtual product at a price point that makes sense. In many cases the customer can purchase a dedicated server for the same or less money. In the end even with ESX and a modified pricing model, VMware would have an extremely tough time competing in the service provider space. "f a virtualization vendor does not enable live migration, host/VM isolation or embrace the concept of a farm, it is not good for production workloads. Virtuozzo does have some of them, but their isolation is not as good as I like to see." While true Windows migration has a small amount of downtime, Linux has a fully live migration. Also please explain the "isolation" you would like to see as that term could me several things. Security wise we are just as secure as other technologies which has been verified by third parties. I assume you mean multi-os support on a single hardware node, but I would argue that isolation is a misleading term for that. Anyhow with all that said I certainly appreciate the article and look forward to hearing more from you on the matter as it only helps to educate the public on the choices they have. Thanks! J
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  • SAS70ExPERT
    One last point. As far as OS support is concerned I would be skeptical of any organizations till running NT4 especially given that it is has long been out of support by Microsoft. Most organizations have already migrated from this platform. Of course windows 2000 is more common (albeit many have already moved to 2k3), however W2K will EOL in about 2 years as well. In the meantime Parallels ships with a P2V tool which allows migrating Windows 2000 physical servers into Windows 2003 containers automatically so you can actually perform an upgrade/consolidation in a single move using a simple tool. Just wanted to make that clear, sorry for the second post :)
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  • SAS70ExPERT
    I currently run Parallels 4 (Virtuozzo) on a HP DL380 G5 Dual Quad Core box. We have on that box 2 MS-SQL 2005 Servers, 1 Advantage Database Server, 2 MS Domain Controllers, as well as MAS90 and this is done with little processor utilization. We also have a second box running 5 other application servers with the same results. Soon we will have more Parallels with 2008 Server. On that we plan on running MS-SQL 2008, a web development server, and Exchange 2007 and I am confident it will handle the load. When we looked at VMware not one vendor would stake their reputation on the ability of VMware to do the job, let alone successfully. I want to make it clear, there is not one virtualization platform today that can do everything. We are also currently evaluating Virtual Iron for possible VDI deployment of 75 desktops and this is due to the isolation abilities. I have many developers and any one of them could bring a single server to a halt. Now consider that Parallels and Virtual Iron can virtualize your environment about as good as VMware and costs a lot less, why would anyone still consider VMware unless you were selling it. Just kidding, it has its place too.
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  • SAS70ExPERT
    Since you mentioned Sun Solaris and Virtuozzo in the same paragraph, and gave the math lesson in you comment - I thought I might mention that both technologies are built on top of the same "free" open source solution - OpenVZ. Sun has done a horrible job in implementation and security. Unfortunately, I believe they ahve too many irons in the fire to do it right. I agree, these are purely vertical solutions and I think the term "virtualization" is loose at best. These are more like chrooted environment O/S's. In your comments, those costs may be above the average costs. Also, many companies may opt to not spend the money on an enterprise supported license for Linux. At any rate, the virtualization providers and Linux Enterprise licenser's in general are going to price Linux right out of the data center. Most of the large data centers that I have had experience with may only license a few key servers to the "Enterprise" contract, and then install the "free" versions on non-impacting environments.
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  • SAS70ExPERT
    Regarding Mark Dean's comment: > Now as for hosting, especially dedicated virtual hosting, one > reason why Virtuozzo is used more is for the simple reason > that VMware will not allow you to run VMs and lease them out > to a third party. If they ever change that, look out. We are a VMware Authorized Hosting Provider and provide this service today! In fact, we have something better... we provide leased resource pools within our shared cluster with SAN storage, which allows a customer to create/destroy VMs at-will and have as many VMs as they wish, only limited by their resources purchased. Snapshots are available as are large volumes (2TB+). CPU and Memory are scalable and a customer can decide to oversell themselves or not if they choose to over-allocate their CPU and Memory to their VMs. Memory de-duplication is done within each physical machine so memory utilized in customers' pools can be quite efficient if, for instance, they have 10 similar Windows Server VMs with 1GB of memory. They may only see a total of 2GB being used since the rest has been de-duplicated. It depends on a number of factors, but the efficiency is definitely gained. Click on my name below in case you are interested in our services. Eric
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