Limitations on Over-Provisioning in XenServer and KVM

12.9.1. Limitations on Over-Provisioning in XenServer and KVM

•In XenServer, due to a constraint of this hypervisor, you can not use an over-provisioning factor greater than 4.

•The KVM hypervisor can not manage memory allocation to VMs dynamically. CloudPlatform sets the minimum and maximum amount of memory that a VM can use. The hypervisor adjusts the memory within the set limits based on the memory contention.

12.9.2. Requirements for Over-Provisioning

Several prerequisites are required in order for over-provisioning to function properly. The feature is dependent on the OS type, hypervisor capabilities, and certain scripts. It is the administrator's responsibility to ensure that these requirements are met.

12.9.2.1. Balloon Driver

All VMs should have a balloon driver installed in them. The hypervisor communicates with the balloon driver to free up and make the memory available to a VM.

XenServer

The balloon driver can be found as a part of xen pv or PVHVM drivers. The xen pvhvm drivers are included in upstream linux kernels 2.6.36+.

VMware

The balloon driver can be found as a part of the VMware tools. All the VMs that are deployed in a over-provisioned cluster should have the VMware tools installed.

KVM

All VMs are required to support the virtio drivers. These drivers are installed in all Linux kernel versions 2.6.25 and greater. The administrator must set CONFIG_VIRTIO_BALLOON=y in the virtio configuration.

12.9.2.2. Hypervisor capabilities

The hypervisor must be capable of using the memory ballooning.

XenServer

The DMC (Dynamic Memory Control) capability of the hypervisor should be enabled. Only XenServer Advanced and above versions have this feature.

VMware, KVM

Memory ballooning is supported by default.

12.9.3. Setting Over-Provisioning Ratios

There are two ways the root admin can set CPU and RAM over-provisioning ratios. First, the global configuration settings cpu.overprovisioning.factor and mem.overprovisioning.factor will be applied when a new cluster is created. Later, the ratios can be modified for an existing cluster.

Only VMs deployed after the change are affected by the new setting. If you want VMs deployed before the change to adopt the new over-provisioning ratio, you must stop and restart the VMs. When this is

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Citrix Systems 4.2 manual Limitations on Over-Provisioning in XenServer and KVM, Requirements for Over-Provisioning
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4.2 specifications

Citrix Systems, a leading provider of virtualization solutions and cloud computing technologies, released version 4.2 of its popular software, Citrix XenApp, which was previously known as Presentation Server. This version marked a significant evolution in providing users with remote access to applications and desktops, emphasizing simplicity, performance, and security.

One of the standout features of Citrix XenApp 4.2 is its improved application streaming capabilities. This technology allows applications to be delivered to users in real-time, reducing the need for extensive local installations and enhancing the user experience. With application streaming, administrators can efficiently manage applications on a central server while ensuring that users have immediate access to the necessary tools.

Another highlight of this version is the enhanced security measures put in place to protect sensitive data. Citrix XenApp 4.2 includes support for SSL encryption, providing a secure communication channel for data transmitted between the server and clients. This is particularly crucial for businesses that need to comply with strict data protection regulations. Additionally, the integration of endpoint security features ensures that unauthorized access to applications is minimized.

Performance enhancements are also a critical focus in this release. Citrix optimized the delivery of applications over various network conditions, ensuring that users experience minimal latency regardless of their location. This was achieved through the incorporation of SmartAccess and SmartControl technologies, which allow administrators to set policies based on user roles, device types, and network conditions. This level of granularity enables organization-wide security without compromising on usability.

The user experience was further improved with a revamped interface, making it easier for end-users to access their applications and data. Simplified menus, clear navigation paths, and the ability to customize user settings contributed to a more efficient workflow, allowing users to focus on their tasks rather than struggling with the software.

Finally, Citrix XenApp 4.2 was designed to be highly scalable. Organizations of all sizes could deploy this solution to deliver applications efficiently, adapting to their specific needs as their user base grows or changes. This flexibility is crucial for businesses looking to future-proof their IT investments while maintaining optimal performance.

In summary, Citrix XenApp 4.2 stands out with its enhanced application streaming, robust security features, improved performance under varying conditions, user-friendly interface, and scalability, making it an ideal choice for organizations seeking to leverage virtualization for remote access to applications and desktops.
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