In this video from ITFreeTraining, I will look at some of the limitations of Hyper-V.
As you will see, these limits are quite high, making Hyper-V a very scalable technology.
In order to run Hyper-V you need to first have a 64bit OS. A 64bit CPU is required and
thus a 64bit OS to go with it. Hyper-V was first added to Windows in Windows Server 2008.
Each OS after this has Hyper-V built-in, but in the case of Windows Server 2008 you need
to be running the Standard, Enterprise or Datacenter edition in order to use Hyper-V.
Windows Server 2012 does not have the Enterprise edition, so you will need Standard or Datacenter
edition to run Hyper-V. For Windows 8 or Windows 8.1 you require the Pro or Enterprise edition.
Microsoft also has a free edition of Hyper-V called Hyper-V Server 2012 R2. This is a free
download and does not cost anything to run. You will, of course, need to correctly license
any OS that runs in a virtual machine on that server.
The Hyper-V edition is a scaled down version of Windows Server, and includes some basic
File and Storage Services as well as the Remote Desktop Services role. Even though it has
the Remote Desktop Services role, the server itself only runs the ‘server core’ interface.
For this reason, the only interface you can use is the command prompt, either by using
the console or from a remote desktop session. You are able to administer the server from
remote, however, using administration tools.
I will next have a look at the hardware limitations of Hyper-V in Windows Server 2012 and Windows
Server 2012 R2. For the host, Hyper-V will support up to 4 Terabytes of memory. If you
run Hyper-V on Windows 8 this will be reduced to 512 Gigabytes as that is all Windows 8
will support.
Next Hyper-V will support 320 logical processors. Logical processors essentially means the number
of cores. So if you are using CPU’s with 4 cores, 320 logical processors would allow
you to have 80 CPU’s in that server.
The next limitation is 2048 virtual processors. A virtual processor is seen by the virtual
machine just like a physical CPU would be seen by a physical computer. These virtual
processors are then assigned to virtual machines of which Hyper-V can support 1024 of them.
The virtual machines are limited to 1 Terabyte of RAM and 64 virtual processors.
You can see that even though there are limitations, the limits are very high and should not cause
any problems to the average administrator. I will now have a closer look at the virtual
machine limitations.
For the virtual machine, the virtual disk is limited to 64 Terabytes using the new VHDX
format. The VHDX format is only available on Windows Server 2012 and Windows 8. If you
are running Hyper-V on an older operating system you will need to use the VHD format
which is limited to 2040 Gigabytes.
Hyper-V supports 4 IDE disks. One of these disks must be the start up disk, in other
words, contains the operating system that you will boot from. If you need more than
4 disks, you can install up to 4 SCSI controllers. Each SCSI controller can have a maximum of
64 disks, meaning that you can have up to 256 SCSI disks in the system. In order to
use SCSI disks, integration services must be installed. Integration services is a collection
of device drivers supplied by Microsoft which, when installed, improves the performance of
virtual machines and allows additional features, like the ability to use SCSI controllers.
Next, each virtual machine supports up to 4 fibre channel adapters. This allows a virtual
machine to connect directly to a physical fibre card installed on the host machine.
The fibre card allows the virtual machine to connect to services like a SAN.
Lastly, each virtual machine supports 12 network adapters. 4 of these network adapters are
legacy network adapters. Legacy network adapters do not have the same performance as the other
type of network adapters; however, they do offer additional support like PXE support,
which allows booting from the network. This covers all the virtual machine limitations.
The last limitation that I will look at is cluster limitations. Hyper-V supports clusters
of up to 64 nodes. One cluster can support up to 8000 virtual machines. There is a limitation
of 1024 virtual machines per server or node. However, if you were to use 8000 virtual machines
they would be spread out amongst the nodes in the cluster.
That’s it for the limitations of Hyper-V. As you can see from this video the limits
are quite high and should not cause any issues for the average administrator. Even with a
limitation of 12 network cards per virtual machine you would have difficulty finding
a physical computer that would support that many network cards so, in some cases, you
can achieve results in virtual machines that would be difficult to achieve with a physical
computer.
Thanks for watching this video on looking at the limitations of Hyper-V. I hope to see
you in other free videos from us in this course and others. Thanks and see you next time.