Home > Hyper-V, Virtualization Basics > Disk and Networking Concepts in Hyper-V

Disk and Networking Concepts in Hyper-V

Hyper-V is Microsoft’s Hypervisor which is shipped as part of Windows Server 2008 Family . In this blog series , I will share my views on Disk and Networking Concepts in Hyper-V .  Hyper-V Server can be managed using tools like Hyper-V manager and SCVMM just like VI Client that is used in vSphere to connect to Host / Virtual Center for management . Installation of Windows 2008 and enabling Hyper-V Role is straight forward and hence will not focus on them .

Introduction to Hyper-V :

Hyper-V is only available on the Standard, Enterprise and Data Center editions of Windows 2008 x64 and Windows 2008 R2 x64 . Windows Server 2008 / Windows Server 2008 R2 can be installed in either a full installation or Server Core installation. Hyper-V can be added as a role in either the full or server core installation. Please remember that full version of Windows Server 2008 cannot be downgrade to the Server Core version and vice versa also holds good. I personally prefer a Server Core Installation over a Full Installation as resource consumption , management overhead , attack surface and patching would be required less .

Virtual Storage Concepts ( VHDs) :

Virtual hard disks encapsulate a guest Virtual machine’s hard disk inside of a VHD file, which is placed on storage space  that is accessible to the host hyper-v server. Using VHDs provides benefits such as the ability to dynamically expand the disk, the ability to take snapshots of the disk, portability in terms of moving the disk to a different server, and so on.

There are three forms of virtual hard disks :

Dynamically Expanding Disks : Dynamically expanding virtual hard disks grows as data is added to the disk and hence consumes less space  . This can be compared to thin provisioning of storage .   The size of the .VHD file does not shrink automatically when data is deleted from the virtual hard disk. To reduce the size of the VHD file , We will have to compact the disk to by using the Edit Virtual Hard Disk Wizard. The dynamic expanding and manual shrinking of the disks may result on additional fragmentation of the host disk.

Fixed Size Disks : Fixed virtual hard disks provide storage capacity that is in the size specified when we create the virtual hard disk . The size of the .VHD file remains ‘fixed’ regardless of the amount of data we store on the VHD . We can use the Edit Virtual Hard Disk Wizard to increase the size of the virtual hard disk. Since we allocate full disk capacity at the time of creation itself , we will not have fragmentation issues at the host .
Differencing Disks : Differencing virtual hard disks provide storage to enable you to make changes to a parent virtual hard disk without altering that disk. The size of the .VHD file for a differencing disk grows as changes are stored to the disk. Different logical servers can share the same parent hard disk and have their own differencing disk for specific changes.

Pass-through : Attach a physical drive / LUN to a VM . Does not support Virtual Machine Snapshots . These are like RDMs that are used in VMware vSphere .

Networks :

We can use Virtual Network Manager to add, remove, and modify the virtual networks. Virtual Network Manager is available from Hyper-V Manager MMC. and also we can use SCVMM to add / remove / modify virtual switches. We can create many virtual networks on the server running Hyper-V to provide a variety of communications channels. Types are as mentioned below :

Private Network : Communications between virtual machines only.
Internal Network : Communications between the virtualization server and virtual machines.
External Network : Communications between a virtual machine and a physical network by creating an association to a physical network adapter on the host server.

It is always recommended to have a dedicated NIC for the Management interface that will be used by the Windows 2008 Root partition .

Integration Components on VMs installed on Hyper-V :

Integrations components (ICs) are sets of drivers and services that help your Virtual Machines have more consistent state and perform better by enabling the guest to use synthetic devices. This can be compared to VMware tools that is mandated in a VMware Environment . Some ICs that come with Hyper-V are VMBUS (transport for Synthetic devices), Time Sync (used to keep VM clocks in sync with the root partition sometimes called the host), Video Driver, Network Driver, Storage Driver. Windows Server 2008 will come with the integration components pre-installed and for all other Guest OS’s Integration components needs to be installed Manually .

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