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Parallels Virtuozzo Containers for Windows best practices and known limitations

Article ID: 112060, created on Aug 25, 2011, last review on Oct 10, 2014

  • Parallels Virtuozzo Containers for Windows


This article describes the best practices and known limitations of Parallels Virtuozzo Containers for Windows technology from an end user's point of view.

The article will help you better understand OS virtualization technology capabilities and choose an appropriate usage scenario for your Parallels Virtuozzo Containers product.

NOTE: You can put the information from this article into every Windows Container in your environment using the BgInfo tool:

113213 How to propagate Parallels Containers for Windows best practices to end customers

Known limitations

Despite the higher densities and faster management operations provided by container virtualization over hypervisor solutions, the fact that containers share the same OS kernel with the host leads to certain restrictions on their use. This section provides recommendations to follow when deploying and maintaining Parallels Virtuozzo Containers for Windows. These recommendations are imposed by the nature of OS virtualization.

  1. Microsoft Updates and Internet Explorer versions

    Parallels Virtuozzo Containers for Windows automatically applies all Microsoft Windows updates that are installed on the physical server to containers. Always use the Windows Automatic Update service on the server to update Windows software. Do not try to perform updates manually or via Microsoft's website. The version of Internet Explorer (IE) must be the same on the physical server as inside all containers hosted on this server.

    NOTE: Customers must not install Windows and IE updates manually. Present the automatic update of containers to customers as one of the main advantages of containers technology.

    Related Knowledgebase articles:

    • 113634: Microsoft Updates and Parallels Virtuozzo Containers for Windows
    • 113428: How to know if an unsupported Microsoft update can be installed on a PVC node
    • 123116: Which Internet Explorer versions are supported on Parallels Containers for Windows?
    • 5605: [Info] Is it possible to create a template of Internet Explorer 7?
    • 7084: How to create an Internet Explorer 8 MUI pack template
  2. Antiviruses

    We recommend installing the required antivirus (AV) solutions on the physical server. Since all containers share the same OS kernel with the host, no antivirus software should be installed inside containers. Antivirus software installed on the physical server detects all viruses inside containers. This provides great savings, as customers only need to install one copy of an AV solution to protect both the physical server and all containers running on it.

    NOTE: Customers must not install any antivirus software inside containers. The service provider should install one copy of the antivirus software on the hardware OS itself.

    Related Knowledgebase article:

    • 9589: Antivirus software compatibility with Parallels Virtuozzo Containers 4.6
  3. Third-party drivers inside containers

    The Parallels Virtuozzo Containers for Windows virtualization core intentionally blocks all untested third-party drivers inside containers for the sake of host security and Hardware Node stability.

    If you want to run an application with custom drivers inside containers, we suggest creating a feature request to Parallels Development via a Parallels Support Ticket to implement and verify the support of the driver.

    Related Knowledgebase article:

    • 8533: A driver installed inside containers is blocked from loading
  4. Complex network software inside containers

    The current version of Parallels Virtuozzo Containers for Windows only supports using the Microsoft Windows VPN inside containers.

    NOTE: CCProxy, OpenVPN, Cisco AnyConnect, Hamachi, and any other non-Micosoft VPN software is not supported inside containers.

    Related Knowledgebase articles:

    • 1601: [Info] Is a VPN client supported inside a VE?
    • 6429: How to start Secure Socket Tunneling Protocol (SSTP) inside a container
  5. VSS backups inside containers

    If a backup solution that uses VSS for creating disk snapshots is installed inside a Virtuozzo container, it cannot create snapshots of the container system drive (C:), only snapshots of its additional drives. We recommend using native Virtuozzo backup tools on the physical server.

    Related Knowledgebase articles:

    • 1968: [Info] Does Virtuozzo 4.0 support any third-party backup solutions?
    • 8527: [Info] Do Virtuozzo 4.5 and 4.6 support any third party backup solutions?
    • 6289: How can I back up and restore data inside containers by means of third-party backup solutions?
    • 111678: Unable to create system state backup of Parallels Virtuozzo Containers server using IBM Tivoli Storage Manager
  6. Application templates:

    There are several limitations for application templates due to the OS-level virtualization design.

    Related Knowledgebase article:

    • 112675: Application template limitations in Parallels Containers for Windows
  7. Microsoft Service packs

    If Parallels Virtuozzo Containers for Windows was installed on Windows Server with some Service Pack (or none), all containers based on this server will run on using the same Service Pack (or none). In this case, neither container provisioning with another service pack nor the according template installation will be possible.

Best practices

  1. General use-cases

    Parallels Virtuozzo Containers for Windows is highly recommended for hosters deploying small- and medium-sized containers that do not run mission-critical applications. The recommended scenarios are:

    • Platform for IIS hosting
    • Platform for Parallels Plesk Panel hosting
    • Remote desktop and VDI (Firefox, MS Office, Skype, Acrobat Reader)
  2. High-availability offerings

    Using the Microsoft Windows clustering software, you can create a Virtuozzo failover cluster consisting of two or more Hardware Nodes and providing failover support for Parallels Virtuozzo mission-critical services and containers. If one Hardware Node in the cluster fails or is taken offline as part of planned maintenance, the services and containers from the problem server are automatically failed over to another Node in the cluster.

    NOTE: Parallels Virtuozzo Containers for Windows technology itself does not provide an SLA greater than 99.5%.

  3. Parallels Virtuozzo Containers for Windows versions

    To use the full power of high-performance servers, Parallels recommends using the 64-bit version of Parallels Virtuozzo Containers 4.6. The 64-bit version can be installed on servers running Windows Server 2008 R2 or the x86-64 editions of Windows Server 2008 and Windows Server 2003.

    NOTE: We do not recommend using 32-bit versions of Windows for resource-consuming containers with web and database hosting. Due to the non-paged pool limitation of 32-bit versions of Windows, the density of containers with web and database hosting servers decreases significantly.

    Related Knowledgebase articles:

    • 1675: [How To] Troubleshooting paged and nonpaged memory pool shortage (Event ID 2019 or 2020)
  4. Parallels Virtuozzo Containers for Windows container parameters

    NOTE: These parameters are approximate and apply to a typical container configuration. Some applications may require higher RAM and numproc limits. Consider application-specific requirements when setting up resource limits for containers.

  5. Memory-hungry applications inside containers

    A container does not have its own paging file and its memory limit defines a portion of the paging file on the server assigned to this container. If customers run a memory-intensive application inside a container, the memory limit for this container must be set high enough to provide optimal application performance. Therefore, the service provider must provide appropriate guidance to the end-customer regarding the intended use and the appropriate level of memory availability for that customer’s VPS.

  6. Backups

    Parallels Virtuozzo Containers for Windows has a native backup tool that allows users to easily backup and restore the entire contents of containers. There is no need to install backup applications inside containers unless the application requires application-level backups (e.g., to restore individual Microsoft Exchange mailboxes). Customers can also use any of the supported third-party backup tools to back up and restore containers.

    NOTE: We highly recommend backing up containers regularly.

    NOTE: Customers do not need to install backup applications inside containers unless they want to create application-level backups. In this case, they need to install a VSS-aware application on an additional drive rather than on the system drive (C). See the Usage Limitations section for more details.

    NOTE: For the best experience with Parallels Virtuozzo Containers for Windows, we recommend backing up large containers to local storage and then transferring the resulting backups to network storage if required.

    NOTE: In addition to incremental and differential backups, we highly recommend creating full backups at regular intervals.

  7. Migration

    Before migrating containers, always make sure that both physical servers have the same set of Microsoft updates and the same version of Internet Explorer installed.

    Related Knowledgebase article:

    • 3591: [Info] OS version compatibility for containers migration
  8. Databases

    We highly recommend using Microsoft SQL or MySQL databases inside containers.

    NOTE: If a customer plans to use other databases inside a container, please ensure that the memory limit for the container is set high enough to provide the optimal database performance.

  9. Microsoft .NET Framework

    Parallels Virtuozzo Containers for Windows itself does not require the .NET Framework to function, which is why it is not necessary to install .NET Framework packages on the Hardware Node to make it work inside containers. If an application inside a container requires the .NET Framework, it will need to be installed directly inside the container.

    NOTE: .NET Framework versions differ among OS versions. Consider the OS compatibility table when installing the .NET Framework:

    111448: How do I properly install .NET Framework inside containers?

  10. Defragmentation

    To achieve the best performance and reduce disk space usage, it is strongly recommended that you perform disk defragmentation for both the Hardware Node and the containers on a regular basis.

    Related Knowledgebase article:

    • 114828: Disk defragmentation in containers best practices

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