Jeff Alexander IT Pro Evangelist Microsoft Australia

Dynamic Memory RemoteFX

How much memory does an IIS server actually need? Print server? File server? Branch Cache? Direct Access? How much will performance be affected if you halved the amount of memory in a VM?

“New virtual machines get 1GB of RAM [no matter what the VM is running]. “All VMs get 4GB of RAM [I have no idea what is happening with that memory] and no one complains” “I take the minimum system requirements and add (insert one: 50%, 100%, 150%)” “A vendor tells me their app needs 4GB of RAM. I do not have the time to test this to find out if it is true or not”

Memory Key factor to the number of running VMs Possibly most expensive asset in system Customer Requirements Improve density, with minimal performance impact Maintain consistent performance Don’t provide a feature that’s unsuitable for production use

Higher VM consolidation ratios with minimal performance impact Dependent on: How much variation in memory utilization the workloads have How good a job you did of sizing the systems in the first place Work well for both server and desktop workloads Add minimal overhead to the system Pass the “that looks right” test

Adding Memory Enlightened fashion Synthetic Memory Driver (VSP/VSC Pair) No hardware emulation Lightweight Removing Memory Wanted to remove memory Ballooning is more efficient Messes up task manager in the guest OS

Benefits Enables higher consolidation ratios per host by addressing the greatest limiting factor to consolidation: Memory A Production feature. Overview Memory is pooled and dynamically and securely distributed across VMs Memory is dynamically added/removed based VM usage with no service interruption Guest enlightened: guests & Hyper-V work TOGETHER

T = 0T = 15T = 30T = 0T = 15T = 30 2 GB 4 GB 6 GB 8 GB Virtual Machines Memory Settings Total System Memory Memory in Use by VMs 8 GB 3 GB Physical Memory Used37.5 % 3 VMs started Finance VM Sales VM Engineering VM

T = 0T = 15T = 30T = 0T = 15T = 30 2 GB 4 GB 6 GB 8 GB Virtual Machines Memory Settings Total System Memory Memory in Use by VMs 8 GB 6 GB Physical Memory Used75 % 3 VMs started Finance starts reports Engineering starts an analysis job Finance VM Sales VM Engineering VM

Memory recovered to allow Service VM 3 VMs started Finance report finished Engineering analysis running IT starts a Service VM Finance starts reports Engineering starts an analysis job Engineering reaches max allocation T = 0T = 15T = 30T = 0T = 15T = 30 Virtual Machines Memory Settings Total System Memory Memory in Use by VMs 8 GB 7.5 GB Physical Memory Used94 % Finance VM Sales VM Engineering VM Service VM 2 GB 4 GB 6 GB 8 GB

Parent Requirements: Windows Server 2008 R2 SP1 Microsoft Hyper-V Server 2008 R2 SP1 Supported Guests: Windows Server 2003, 2008 & 2008 R2 Enterprise and Datacenter Editions only 32-bit & 64-bit versions Windows Vista and Windows 7 Enterprise and Ultimate Editions only 32-bit & 64-bit versions

Cache to improve performance Windows Memory Manager utilizes all free memory for cache

Guest Applications HypervisorHypervisor User Mode Kernel Mode DM VSC VMWPVMWP Window s Memor y Manage r VMBusVMBus VMMSVMMS VMBusVMBus VIDVID WP Memory Management Windows Memory Manager DM VDEV / VSP DM Memory Balancer Interface Memory Balancer Windows Memory Manager VIDVID

Collect / Send guest memory statistics to the balancer Add / Remove memory to the guest Enlightened Memory Addition Lightweight & fast No hardware emulation Memory Removal by Ballooning

Orchestrate all Hyper-V memory operations Live Migration Optimization: Shrink the memory of the VM on the source node Shorter migration times

VID Virtualization Infrastructure Driver Manages the mapping of VM memory => Physical Memory Utilizing Windows Memory Manager to clean memory Utilizing Windows Memory Manager to decrease fragmentation

Single place for all memory decisions Calculates Memory Demand Protects host from resource starvation Ensures a stable system with minimal operations

Host Reserve is automatically calculated based on: Total memory size of the host SLAT capability of the host NUMA architecture of the host ~ 400 MB + (0.03 * Total Memory Size of the host) Optimally distributed across NUMA nodes VM Reserve Host Reserve

When there is available memory on the host, VMs get their target memory Root Reserve Root Reserve Memory Demand Buffer Available Memory Available Memory Memory Demand Buffer Target Memory

When there is no available memory on the host, weight is used to determine memory distribution Root Reserve Root Reserve Hyper-V Host VM1 Low Weight VM2 Medium Weight VM3 High Weight Memory Demand Buffer Memory Demand Buffer Memory Demand Buffer Priority Penalty Buffer Target Memory

Goal: Stable System / Minimal Overhead Active memory addition policy Memory is added immediately when VM needs it Passive memory reclamation policy Memory is not removed when there is no immediate need Unutilized memory is collected every 5 minutes

Availability is a concept How much memory does the VM have? How much memory does the VM want? The difference is the availability Priority: which VM gets the memory first 1-10,000: default is 5,000 The higher the priority, the higher the availability

Hyper-V has always had the concept of a reserve of memory that is kept for the parent partition DM allows VMs to push up against the reserve consistently New behavior to better protect the parent partition from rampaging virtual machines New registry key in place May result in less memory being available for VMs

Memory Over-Commit (Technology) General name for VMWare Memory Management Technologies Memory Over-Commit (Resource) Subscribing more memory to your VMs than the physical memory on the host VMWare / Microsoft agree: Memory Resource Over-Commit is a bad thing

What about numbers? Based on the configuration What matters is how much memory VM needs? Login VSI VDI workload demand ~400 / 600 MB Previous Memory Size = 1 GB; Saving 40% Previous Memory Size = 2GB; Saving 75%

VMWare: Doesn’t trust guest information Users need to guess a memory size VMs start with large memory values Then memory is saved (!) with different technologies Hyper-V Collaborates with guest Automatic sizing of VMs Memory Thin Provisioning

Enhancements to scalability and high availability when using DirectAccess addition of support for 6to4 and ISATAP addresses when using DirectAccess in conjunction with Network Load Balancing (NLB) Support for Managed Service Accounts (MSAs) in secure branch office scenarios SP1 enables enhanced support for managed service accounts (MSAs) to be used on domain-member services located in perimeter networks

Support for increased volume of authentication traffic on domain controllers connected to high- latency networks SP1 allows for more granular control of the maximum number of possible concurrent connections to a domain controller

TAP program workload list: SQL / AD / DNS / Print Server / File Server / IIS / LoB Apps / RDS / Win7 VDI / DA / DHCP / Exchange (Non- Mailbox Roles) / TMG 2010 / SPS 2010 / App-V / Med- V / OCS / FTP / WDS / … TAP program workloads not utilizing DM: Linux VMs Exchange 2010 Mailbox Role

Workloads that require tuning = Apps doing cache management (SQL / Java / …) Memory Buffer = 5% App Minimum Memory < DM Startup Memory App Maximum memory < DM Maximum Memory

Official SQL Server Statement: Q7: Is Hyper-V Dynamic Memory supported for SQL Server? A7: Hyper-V Dynamic Memory is fully supported with SQL Server. Only SQL Server versions and editions (Enterprise and Datacenter) that support Hot Add Memory can see memory that is added by using Hyper-V Dynamic Memory. SQL Server versions that do not support Hot Add Memory are still supported. But these versions will detect only the memory that is present in the operating system when SQL Server starts. Before you deploy Hyper-V Dynamic Memory, please read the following resources when you use Hyper-V Dynamic Memory with SQL Server: Hyper-V Dynamic Memory Evaluation Guide SQLOS Team Blog - Hyper-V Dynamic Memory Windows Virtualization Team Blog - Dynamic Memory

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SQL and Dynamic Memory Configuration Virtualization Team Blog Dynamic Memory Configuration Guide us/library/ff817651(WS.10).aspx