Virtual Hard Drives - Research Paper Example

Virtual Hard Drives (VHD) Introduction Virtual Hard disk is a separate disk image ‘file format’ that canstore the contents of the physical hard drive, partly or fully. The creation can be done at a location that is preferable to the computer host. The VHD has all the structural elements of the physical hard disk, while it can contain almost all the data from the hard disk, by copying the data files or simply creating new data resources. The types of virtual hard disks include the fixed size and the disk that can have dynamically expanding size. Yet another type is the differencing one, which can be attached to any of the two other types, for increasing the performance of the system. The fixed sized disks do not have to specify for the minimum space required on the computer file system of the host, as it can automatically acquire the required space. On the other hand, dynamically expanding VHDs will take up the required space, according to their need. (Rouse) Virtual Hard Disk drives are the best alternative, when conducting cost-effective operations on computer systems. Using VHD, diverse operating systems can be loaded on the same PC, which allows the host to run different software programs on the same computer, while allowing the software developers to test their programs in a cost-effective manner. During February, 2013 Microsoft purchased the Virtual Hard Disk software from Connectix Virtual PC Software, which was originally responsible for creation of this software. Thereafter, Microsoft renamed this product as Microsoft Virtual PC. (VHD) Virtual Hard disk Formats Apart from the fixed and dynamic formats, as mentioned above, there is another format of VHD called ‘Differencing’ type. Each format can perform different tasks, as they vary in performance. Fixed size VHD The space required by this type of VHD is allocated on the physical Hard disk storage, while creating the VHD. While the fixed size can be increased, in an offline operation, the software does not support reducing the size. The fixed size characteristic of this type ensures optimum efficiency in operation of the system. However, due to the commitment of space allocated, it cannot be used by the physical drive, incase the VHD does not utilize any portion of the given space. Dynamically expanding VHD This file format counters the disadvantage of the fixed type VHD, as the space utilized by dynamically expanding VHD will depend on the actual requirement for the data size that is being written to it. However, ‘on-disk meta-data’ size will add to this requirement. The file size can vary from as small as 43 KB in a VHD of this type to 20GB. The choices of optimization of performance are available with this type of VHD. However, the performance can be slower, for read or write functions, than the fixed size type VHDs. Differencing VHD This type of VHD can be associated with either of the above two types. While they can implement many additional features to their parent VHD, they also are responsible for prevention of any changes to the parent hard drive. The advantage of using this type is that space taken from physical hard drive can be reclaimed by compacting a differencing VHD.(Ranjana1) Native VHD boot Native boot VHD configuration is available in Windows 7 and Windows server 2008 R2. This allows the user to use the VHD as the computer running operating system without requirement of any parent system or hypervisor. In addition, Native boot provides full access to all the files in the PC system, as the virtual volumes are visible, after the VHD portions are automatically attached to the system. Native VHD boot supports all the tree types of VHDs. However, the system will fail in case the expanding VHD requires more than the space available with the physical host drive. Only BIOS-based and UEFI-based firmware supports Native VHD boot. (Frequently Asked Questions) VHD vs. VHDX Windows Server 2012 has made available another VHD format, called VHDX. It has many advantages. The main benefit is towards creating very large virtual hard disks, up to the size of 64TB. Big data base applications and large workloads can be virtualized by using VHDX. Using 4KB logical sectors, the applications for such sector drives perform efficiently, in a better manner. VHDX provides additional protection against data corruption and dynamically expanding VHDs can perform better in case of any power failures. This file format has better alignment, which makes it feasible to work with large sector drives as well. Hyper-V on Windows Server 2012 has, by default, the choice of VHDX, when creating a virtual hard disk, on such system. By opting for the default choice, the user can avail the above benefits of VHDX file format. (Tulloch) Options for storing VHDs There are three options for storing VHDs. The first option is simple, which facilitates storing in local volumes, like direct-attached storage system. The second option is storing in network volumes, like network-attached storage. The third is SAN, the storage area network. The direct-attached storage is the best option for servers that host only a few virtual machines. However, the disk resources are limited here, as all VMs on the particular server will compete with each other for getting the available disk resource. Network-attached storage option can be utilized only if it is used with Hyper-V. Although the storage area network, being the network-based technology, is very expensive, it performs better than the other two storage options.(Posey) Conclusion Virtual Hard Disk file format is the latest technology product available from Microsoft, as the organization named it as ‘Virtual PC’. There are many advantages of creating a VHD, particularly when the same is of dynamically expanding type. This file format does not require the full space and resources from the physical hard drive, as the allocation is need-based. The data used for writing on this file format takes automatically the space required for that particular task only. The remaining resources remain free. On the other hand, in fixed VHD format, the space once allocated to such VHD cannot be used by the physical drive, even if it remains unutilized by the particular VHD. Works Cited “Frequently Asked Question: Virtual Hard Disks in Windows 7 and Windows Server 2008 R2”, Microsoft Windows. Oct, 2010, Web. 02 Nov. 2013. Posey. M. Brien “Setting up virtual Hard disk storage.” Search virtual Desktop, nd. Web. 02 Nov. 2013 Ranjana1, “Virtual Hard Disk (VHD) Architecture Explained.” Simplifying Windows, 23 March, 2010. Web. 02 Nov. 2013. Rouse, Margaret. “Virtual Hard Disk (VHD).” Search virtual desktop, July, 2009. Web. 02 Nov. 2013. Tulloch, Mitch “How to Choose the Right Virtual Disk Format”, Biztech magazine. 20 Sep., 2010, Web. 02 Nov. 2013. “VHD.” Computer Hope, nd. Web. 02 Nov. 2013 Read More