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The maximum number of hosts and virtual machines tested with and supported by VMM on the highest recommended hardware configuration is 400 hosts and 8,000 virtual machines.

If your VMM implementation has over 150 hosts, we strongly recommended that you enable server-optimized garbage collector (GC) on the VMM server instead of the default workstation garbage collector. This can significantly reduce the CPU utilization on the VMM server and improve your performance for parallel VMM operations.

To enable server-optimized garbage collector (GC) on the VMM server, create a file that is named vmmservice.exe.config by using the following code, and then for VMM 2008, place it into the %SYSTEMDRIVE%\Program Files\Microsoft System Center Virtual Machine Manager 2008\Bin directory on the VMM server, or for VMM 2008 R2, place it into the %SYSTEMDRIVE%\Program Files\Microsoft System Center Virtual Machine Manager 2008 R2\Bin directory on the VMM server..

<configuration>

   <runtime>

      <gcServer enabled="true"/>

   </runtime>

</configuration>

The number of virtual machines that can be run on a host is primarily limited by the configuration of the host and of the virtual machines on the host.

 

 

The minimum and recommended hardware requirements for the VMM server depend on the number of hosts that you manage and whether you use the same computer for the VMM server, the VMM database, and as a library server.

 

 

The minimum and recommended hardware requirements to install and operate all VMM components on a single computer are listed in the following tables based on the number of hosts that you manage.

From 5 to 10 hosts

 

Hardware component	Minimum	Recommended
Processor	Pentium 4, 2 GHz (x64)	Dual-Core Pentium 4, 2 GHz (x64) or greater
RAM	2 GB	2 GB
Hard disk space	10 GB	40 GB

 

From 11 to 20 hosts

 

Hardware component	Minimum	Recommended
Processor	Pentium 4, 2.8 GHz (x64)	Dual-Core Pentium 4, 2.8 GHz (x64) or greater
RAM	2 GB	4 GB
Hard disk space	10 GB	50 GB

 

Managing up to 150 hosts

 

Hardware component	Minimum	Recommended
Processor	Pentium 4, 2 GHz (x64)	Dual-Processor, Dual-Core, 2.8 GHz (x64) or greater
RAM	2 GB	4 GB
Hard disk space (without a local VMM database)	2 GB	40 GB
Hard disk space (with a local SQL Server 2005 Express Edition database)	10 GB	50 GB Note For the SQL Server 2005 Express Edition, the database size is limited to 4 GB.
Hard disk space (with a local, full version SQL Server 2005 database)	80 GB	150 GB

 

If you also use the VMM server as a library server, you need to provide additional hard disk space for storing objects. For more information about the hard disk space requirements for the VMM library, see System Requirements: VMM Library Server.

Managing more than 150 hosts

 

Hardware component	Minimum	Recommended
Processor	Pentium 4, 2.8 GHz (x64)	Dual-Processor, Dual-Core, 3.6 GHz or greater (x64)
RAM	4 GB	8 GB
Hard disk space	10 GB	50 GB

 

For better performance, when you are managing more than 150 hosts, it is recommended that you use a dedicated computer for the VMM server and do the following:

·      Add one or more remote computers as library servers and do not use the default library share on the VMM server.

·      Use a remote, full version of SQL Server for the VMM database.

 

 

SCVMM Administrator’s Console Rollup

Attention :

Restart requirement

After you apply this hotfix, you must restart the computer.

List of issues that are resolved:

• If a VM is configured to have 3 virtual processors, the SCVMM Admin Console crashes.
  
  Note To resolve this issue, install the hotfix rollup package 982522 that is a hotfix rollup package for System Center Virtual Machine Manager 2008 R2 and then this hotfix rollup package.  
• This hotfix rollup package also resolves the issues that are documented in the following SCVMM 2008 R2 Admin Console update:
  976246 When you remove a virtual hard disk from a virtual machine in System Center Virtual Machine Manager 2008 R2, the .vhd file on the Hyper-V server is deleted without warning

How to obtain the SCVMM 2008 R2 Admin Console hotfix rollup package

This hotfix rollup package is available on Microsoft Update.
To obtain this update from Microsoft Update, follow these steps on computers that have the SCVMM Admin Console installed:

1. Click Start, and then select Control Panel.
2. In Control Panel, double-click Windows Update.
3. In the Windows Update window, click Check Online for updates from Microsoft Update.
4. Click important updates are available.
5. Select Update for System Center Virtual Machine Manager 2008 R2 (KB982523), and then click OK.
6. Click Install updates.

To manually download the hotfix rollup package from the Microsoft Update Catalog, visit the following Microsoft website:

http://catalog.update.microsoft.com/v7/site/Search.aspx?q=982523

To manually download the hotfix rollup package from the Microsoft Update Catalog, visit the following Microsoft website:

To install this hotfix rollup package that can be downloaded from the Microsoft Update Catalog on the Virtual Machine Manager server, follow these steps:

1. Extract the VmmClient32Update.cab or VmmClient64Update.cab file to a temporary directory.
2. Open an elevated command prompt, type the following command for the 32-bit package, and then press ENTER to install the update:
   msiexec /update vmmClient32Update.msp BOOTSTRAPPED=1
   

   Note For the 64-bit package, type the following command:

   msiexec /update vmmClient64Update.msp BOOTSTRAPPED=1

Hotfix rollup package information

Prerequisites

To apply this hotfix, you must have SCVMM Admin Console installed.

 

 

List of issues that are resolved:SCVMM Server Rollup

Issue 1: A high availability virtual machine with a GPT pass-thru disk is reported is reported as “Unsupported Cluster Configuration.” 

Issue 2: When you manage VMware Virtual Center that has distributed switches, the Virtual Machine Manager service (Vmmservice.exe) crashes.

Issue 3: After Quick Storage Migration is completed, the Failover Cluster Management MMC snap-in reports that the VM still uses the old CSV volume.

Issue 4: If a VM is configured with 3 virtual processors, the SCVMM Admin Console crashes.

Issue 5: The settings for the virtual network are incorrect after a Refresh-VMHost cmdlet job is completed.

How to obtain this SCVMM 2008 R2 hotfix rollup package

This hotfix rollup package is available on Microsoft Update.
To obtain this update from Microsoft Update, follow these steps on the Virtual Machine Manager server:

1. Click Start, and then select Control Panel.
2. In Control Panel, double-click Windows Update.
3. In the Windows Update window, click Check Online for updates from Microsoft Update.
4. Click important updates are available.
5. Select Update for System Center Virtual Machine Manager 2008 R2 (KB982522), and then click OK.
6. Click Install updates.

Note If the Virtual Machine Manager or Virtual Machine Manager Agent service is running when the hotfix rollup package is installed on the Virtual Machine Manager server, you have to restart the computer

To manually download the hotfix rollup package from the Microsoft Update Catalog, visit the following Microsoft Web site:

http://catalog.update.microsoft.com/v7/site/Search.aspx?q=982522

 

 

 

 

 

 

 

 

If you get this error in SCVMM and your hosts are managed on the perimeter network, this is caused due the Host on a Perimeter Network that was previously able to communicate with the System Center Virtual Machine Manager 2008 server no longer can.

 

A manual refresh of the host will result in a job failure as shown here:

 

 

 

 

 

Quick fix:

 

 

 

Here are some recomendations about how you should size VM memory :

You must size it to reasonably handle the expected load at ordinary and peak times because insufficient memory can significantly increase response times and CPU or I/O usage.

When running Windows in the child partition, you can use the following performance counters within a child partition to identify whether the child partition is experiencing memory pressure and is likely to perform better with a higher VM memory size:

Performance counter	Suggested threshold value
Memory – Standby Cache Reserve Bytes	Sum of Standby Cache Reserve Bytes and Free and Zero Page List Bytes should be 200 MB or more on systems with 1 GB, and 300 MB or more on systems with 2 GB or more of visible RAM.
Memory – Free & Zero Page List Bytes	Sum of Standby Cache Reserve Bytes and Free and Zero Page List Bytes should be 200 MB or more on systems with 1 GB, and 300 MB or more on systems with 2 GB or more of visible RAM.
Memory – Pages Input/Sec	Average over a 1-hour period is less than 10.

 

 

Correct Memory Sizing for Root Partition

The root partition must have sufficient memory to provide services such as I/O virtualization, snapshot, and management to support the child partitions. The root partition should have at least 512 MB available. Using Server Core in the root partition leaves additional memory for the VMs to use (approximately 80 MB for commit charge on 64-bit Windows).

A good standard for the memory overhead of each VM is 32 MB for the first 1 GB of virtual RAM plus another 8 MB for each additional GB of virtual RAM. This should be factored in the calculations of how many VMs to host on a physical server. The memory overhead varies depending on the actual load and amount of memory that is assigned to each VM.

 

 

 Patching and or Updating a Windows 2008/R2/Hyper-V Physical Host requires a close attention to the minimal details.

 Specially in production environment as we are talking not only to Microsoft patch/updates but also Industry products such as Lan cards drivers, Bios, Software Agents, firmwares, it’s important for you to remember that the updates are required only under certain circumstances ( e.g  updating you Network Lan Driver could let you to lose the Virtual Switchs Networks ).

 

Some recomendations :

 

1. Reduce/avoid some updates by using the Core Version. It’s my favorite version and not only because of this reason but also because it uses a lower resources translating in more CPU/memory to the VMs.

 

2. Only download updates that are available on Windows Update, as well those that are available at the Microsoft Download Center and Vendors Websites. NEVER, NEVER use DRIVERS/FIRMWARES from others sources. My recomendation is always go to the Vendor website to get the most updated driver/firmware. Don’t even think about downloading it from others sites/p2p networks. Why ? Simple, it could contain virus/worms and modified code.

 

2. PLAN : You might need a reboot of the Physical Production Host ( If you already implemented Live Migration, nothing to be worried : just move the VMs to another Hyper-V host . If not, it’s time for you to revise your downtime plan )

 

3.  Change the Windows Update Settings to Check for Updates and to let you choose which one is necessary.

 

 

Comprehensive list of Hyper-V R2 updates