Hyper-V Server virtual hard disk

What is a virtual disk? What are the characteristics of virtual disks in Windows Server R2?

A virtual disk is a separate file that is placed on a physical hard disk. The purpose of the virtual disk file is to capture the full state of the virtual machine residing in the server's memory and display the information in a clear disk file format. Windows Server R2 and Hyper-V use the virtual hard disk (VHDX) file format, which is the file name extension for virtual hard disks. VHDX.

Virtual hard disks are the key to virtualization. When a server is powered on, each virtual machine is loaded into server memory and started from its corresponding VHDX file. As virtual machines run, VHDX files can be updated to reflect data or state changes. VHDX files can be copied to remote Storage to provide backup and disaster recovery copies of virtual machines. VHDX files can also be migrated or replicated to other servers, allowing virtual machines to be migrated or replicated in the event of software licensing. Virtual hard disks are also suitable for centralized storage (instead of being present on each local server).

The virtual hard disk format continues to evolve to meet the changing needs of virtual machines and data center resources. One obvious change is that the VHDX size has increased from 2TB to 64TB, and can receive huge virtual machines and data resources. This can make the virtual disk more suitable for applications such as database or memory analysis.

Even with carefully designed redundancy, batteries, and backup power supplies, accidental power outages can always cause the server to crash, damaging storage data-especially data that changes periodically, such as virtual disk files. The VHDX format now records all of the VHDX metadata changes. Windows Server R2 allows you to create a split disk so that a VHDX file can record changes to other files. All changes are tracked, so unnecessary or problematic changes can be recovered. The combination of this functionality allows the virtual server to maintain little (if any) data or state loss when recovering a virtual machine.

The VHDX format also introduces a variety of features that enhance performance. For example, the VHDX has greater storage capacity than the old VHD format. It also provides data corruption protection during power failure and optimizes the structure alignment of dynamic and differencing disks to prevent performance degradation on new large sector physical disks.

One, Hyper-V virtual hard disk format:

Virtual hard disks provide storage space for virtual machines, where virtual hard disks are functionally equivalent to physical hard disks and are used by virtual machines as physical hard disks. Microsoft offers two types of virtual hard disk formats, namely VHDs and VHDX. Prior to Windows Server 2012, the Hyper-V virtual hard disk format was primarily. vhd format, which exceeded the 2TB limit, supported up to 64TB, and Microsoft's recommended virtual hard disk format. The main features of the VHDX format are as follows:

1) Maximum support 64TB storage capacity.

2) logs that update the VHDX metadata structure can be logged. This provides better resiliency for VHDX files in the event of a power outage.

3) enables larger block sizes for dynamic and differential disks, allowing the disk to better meet virtualized load requirements.

4) improves application and load performance, especially on physical disks that have a sector size greater than 512 bytes.

5) Support for storing custom metadata. For example, you can record the operating system version, or the patch information that has been installed.

6) Use Windows PowerShell commands on the computer running Hyper-V to configure and manage the virtual disks.

7) In the virtual hard disk format alignment, you can work better on large sector disks.

8) efficiently represent data (also known as "clipping"), making file sizes smaller and allowing the underlying physical storage device to reclaim unused space. (Crop the physical disks that need to be connected directly to the virtual machine or SCSI disk and the trimmed-compatible hardware.) )

Second, the virtual hard disk type:

Windows Server 2012/R2 mainly provides four types of virtual hard disks: fixed size, dynamic expansion, differential disk, and passthrough hard drives.

1) Fixed size: This type of disk provides better performance and is recommended for servers running applications with advanced disk activity. The virtual hard disk file that was originally created uses the size of the virtual hard disk and does not change when data is deleted or added.

2) Dynamic expansion: This type of disk can make better use of physical storage space and is recommended for servers that do not contain dense disk-intensive applications. A virtual hard disk is small when it was originally created, but becomes larger as data is added to it.

3) differencing disk: This type of disk has a parent-child relationship with another disk that you want to keep, and you can make changes to the data or operating system without affecting the parent disk so that changes can be easily restored, and all the child disks must have the same virtual hard disk format (VHD or VHDX) as the parent disk.

4) Straight-through drives: straight-through disks provide a way to connect Hyper-V virtual machines to physical storage (as opposed to relying on virtual hard disks). However, it is important to note that the use of straight-through disks has some limitations. Straight-through disks are popular before Windows Server 2012 is released. At the time, Hyper-V used a virtual hard disk (VHD) format of up to 2TB, which was not enough for some virtual machines (VMS). A straight-through disk bypasses the 2TB storage limit and is popular. However, in Windows Server 2012, Microsoft introduced the VHDX virtual hard disk format, which is no longer restricted to 2TB. In many scenarios, the use of VHDX-based virtual hard disks reduces the need for straight-through disks. If you intend to use a straight-through disk, you need to know that these disks are bound to the host server. Therefore, using a straight-through disk will complicate the live migration (although setting up a straight-through disk to a VM-dependent cluster disk can make live migration possible). In addition, Hyper-V cannot take a snapshot of a straight-through disk.

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C. Supported Drive types:

Hyper-V deployed virtual machines support the storage types of mainstream vendors in the market, including Das, NAS, Fcsan, Iscsisan. Device types include IDE devices and SCSI devices:

1) IDE device: Hyper-V uses an analog device with an IDE controller. You can have up to 2 IDE controllers, each of which can have 2 disks.

2) SCSI devices: Each virtual machine can support up to 256 SCSI devices (4 SCSI controllers, with a maximum of 64 disks per controller). The SCSI controller uses a device developed specifically for virtual machines and communicates using the virtual machine bus.

Iv. Create a virtual hard disk:

1) Click "New" in the Hyper-V Server global settings to select the disk

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2) Select the disk format, as described above, Hyper-V supports two virtual hard disk formats, and Windows Server 2012 starts with the VHDX format by default

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3) Select the disk type and select a fixed size here.

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4) Specify a name and location

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5) Configure virtual disk space size

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6) Click Finish, wait for creation to complete

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7) Open Windows Explorer to view the created virtual disk

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Add the pass-through hard drive to the virtual machine. Open Disk Manager to view unused physical disks

1. Right-click the virtual machine "bj-ap-01" and select settings

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2. Click on the SCSI controller, click on the hard drive, click Add

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3. The new Hard disk page that appears click on the physical disk and specify the available physical disks, click Apply

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4. Log in to the virtual machine "bj-ap-01" and open the Disk Manager, at which time you can see the new disk

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Hyper-V Server virtual hard disk