RAM PRESSURE SETTINGS WINDOWS
The paging operation in the guest operating system is performed by Windows Memory Manager. When host memory is oversubscribed, Hyper-V continues to rely on the paging operation in the guest operating system because it is more effective than Smart Paging. Oversubscribing memory for a running virtual machine is required.Ī virtual machine is failing over in Hyper-V clusters. No memory can be reclaimed from other virtual machines running on the host.Ī virtual machine is being started from an “off state” (instead of a restart). To minimize the performance impact of Smart Paging, Hyper-V uses it only when all of the following occurs:
RAM PRESSURE SETTINGS INSTALL
Ensure the Startup-RAM value meets the minimum memory requirements of the operating system during the install or upgrade procedure. Even if Dynamic Memory has been configured for the virtual machine, the virtual machine only uses the amount of memory as configured in the Startup RAM setting. When installing or upgrading the operating system of a virtual machine, the amount of memory that is available to the virtual machine during the installation and upgrade process is the value specified as Startup RAM. However, it can degrade virtual machine performance because disk access speeds are much slower than memory access speeds. It provides a reliable way to keep the virtual machines running when there is no available physical memory. This approach has advantages and drawbacks. This memory management method uses disk resources as additional, temporary memory when more memory is required to restart a virtual machine. To provide a reliable restart experience for the virtual machines configured with less minimum memory than startup memory, Hyper-V uses Smart Paging. Minimum memory configuration with reliable restart operationĪs in the previous version of Dynamic Memory, you can configure a minimum memory amount for virtual machines, and Hyper-V continues to ensure that this amount is always assigned to running virtual machines. Smart Paging is used to bridge the memory gap between minimum memory and startup memory, and allow virtual machines to restart reliably. This can cause sporadic virtual machine restart failures. Due to host memory pressure or virtual machine states, Hyper-V may not always have additional memory available.
If a virtual machine has a smaller amount of memory than its startup memory and if it is restarted, Hyper-V needs additional memory to restart the virtual machine. Although minimum memory increases virtual machine consolidation numbers, it also brings a challenge.
Windows Server 2012 also introduces Smart Paging for reliable virtual machine restart operations.
This is reflected as increased virtual machine consolidation numbers, especially in Virtual Desktop Infrastructure (VDI) environments.
In Windows Server 2012, Dynamic Memory introduces a minimum memory setting, which allows Hyper-V to reclaim the unused memory from the virtual machines. As a result, administrators sometimes assign extra memory to a virtual machine because Hyper-V cannot reclaim memory from these virtual machines after startup. However, Windows requires more memory during startup than the steady state. Technical overviewĭynamic Memory, introduced in Windows Server 2008 R2 Service Pack 1 (SP1), defined startup memory as the minimum amount of memory that a virtual machine can have. Dynamic Memory run-time configuration changes can reduce downtime and provide increased agility to respond to requirement changes. This can lead to lower costs, especially in environments that have many idle or low-load virtual machines, such as pooled VDI environments. With the Dynamic Memory improvements for Hyper-V in Windows Server 2012, you can attain higher consolidation numbers with improved reliability for restart operations. You also gain agility in responding to requirement changes with these new capabilities. If you have idle or low-load virtual machines, as in pooled Virtual Desktop Infrastructure (VDI) environments, Dynamic Memory enables you to increase consolidation and improve reliability for restart operations. Applies To: Windows Server 2012 R2, Windows Server 2012
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