What’s New in Windows 8 for Hyper-V Based Cloud Computing (Part 4) - Hyper-V Storage Features

by [Published on 1 March 2012 / Last Updated on 1 March 2012]

In this article, you learn about new storage features in Windows Server 8 that Hyper-V can leverage to provide highly scalable and highly available cloud environments.

If you would like to read the other parts in this article series please go to:

Windows Server 8 Storage

In Windows Server 8, Microsoft enhances the platform to provide an even more feature-rich, resilient, and highly-available software core for the deployment of private and public clouds in large enterprises. In parallel, there are also new features in Windows Server 8 that lower the technological complexity, decrease the need for multi-vendor solutions, and reduce the cost to deploy private clouds in small to medium size organizations with limited IT staff and expertise. Windows Server 8 storage is one of the primary areas where many new features abound to enhance the architecture and performance of large cloud deployments, while also providing access to advanced storage features using inexpensive off-the-shelf components.

NTFS Enhancements

With the ever-growing amount of data that organizations generate and to which they require dependable access, it is critical for storage devices to provide a high level of data integrity and availability. However, it is not only the hardware devices themselves that must meet a high level of dependability; this is especially true for the file system that controls the format and movement of data between the application and the storage devices.

In Windows Server 8, NTFS data integrity is enhanced to function more reliably with industry standard storage such as SATA, and to maximize file system availability. In the past, some access functions did not behave as expected and resulted in data corruption during system crash events. In order to mitigate this problem, NTFS now flushes the disk cache when it is necessary to maintain the write order and keep the data on disk consistent. This enhancement decreases the possibility of data inconsistency caused by events such as an unexpected power loss while still enabling disks to cache data as long as safely possible to ensure high performance levels.

Another NTFS enhancement is found in the separation of the file system corruption scan functionality from the repair functionality which, in previous versions, occurred sequentially using the Chkdsk utility, and could require a volume to be offline for a significant period of time. In Windows Server 8, a file system scan runs in the background to identify and log specific file system corruption. The file system need only be taken offline to repair identified corruption, resulting in downtime that is proportional to the number of corruptions, rather than volume size. Just as in Windows Server 2008, some corruption cases are repaired while a volume is online. In fact, Windows Server 8 is able to do this for a larger number of cases, further maximizing file system availability.

Storage Pools and Storage Spaces

Windows Server 8 introduces two new platform abstractions: Storage Pools and Storage Spaces. Storage pools are units of aggregation that allow you to take a set of industry standard disks connected through either SAS or SATA, and to pool the disk space into a larger aggregate set that can be administered as a single component. Disks in a pool do not have to be identical, and a pool can be created across disks with different aspect ratios. A storage pool can also be connected to a single system or shared across multiple systems. Additionally, storage pools can be created and managed using PowerShell scripts.

Storage spaces allow the definition of virtual disks that are carved out of a storage pool, and that are embedded with a set of attributes used to define state characteristics such as availability and provisioning level. Multiple storage spaces can be created from a single storage pool.

Storage spaces can be thin-provisioned to grow allocated space from a storage pool as storage space is consumed. An administrator can configure a storage space that is larger than the underlying pool, and grow the pool as needed. When a storage pool is nearing full utilization, a notification is issued and an administrator can simply add more physical drives to the storage pool. If storage is released through the deletion of files or data, storage spaces can shrink and return storage to the storage pool. Storage spaces can be used to support clustering, file servers, Hyper-V, and applications such as SQL Server.

Storage spaces support mirroring and parity to provide data redundancy and resiliency. If a storage space is configured with mirroring, data can be duplicated 2 or 3 times, as selected. In this configuration, all available spindles in the space are used to maximize performance. In the case of parity, single parity support (with journaling) is provided. 

Windows Server 8 supports delegation of access to restrict administrative control to only specified pools or spaces. Storage spaces can be managed using PowerShell scripts.

Storage Optimization

Windows Server 8 provides a storage optimizer that runs during system idle cycles to consolidate and compact file system data and return free space to storage devices. The storage optimizer is implemented to function without user intervention.

Data deduplication

Data deduplication in Windows Server 8 is implemented on a volume level to optimize the usage of storage space. Data deduplication is transparent to the primary workload on the server as it minimizes I/O impact through scheduled and selective optimization. High data integrity is achieved by performing data integrity validation on all data as well as metadata. Duplicate data is detected and removed from files and placed in a separate store that is accessible to all files. Data redundancy and resiliency is achieved for all metadata as well as often-used data chunks. Administrators can control which files are deduplication targets.

Offloaded data transfer

Windows Server 8 provides the offloaded data transfer feature to shift the processing load associated with moving data between host storage devices to smart storage controllers, if available. For example, a traditional data transfer between two different hosts requires the following steps:

  • The source host accesses the source storage device and transfers the data into memory
  • The source host establishes a connection to the destination host
  • The source host transfers the data to the destination host
  • The destination host accesses the destination storage device and transfers the data from memory to the storage device

If the storage devices connected to the source and destination hosts support offloaded data transfer, the data transfer process requires the following steps:

  • The source host requests a token (from the source storage device) that represents the data set
  • The source host establishes a connection to the destination host
  • The source host transfers the token to the destination host
  • The destination host sends the token to the destination storage device
  • The source and destination storage devices establish a connection and perform the actual data transfer

With offloaded data transfer, there is minimal impact to the source and destination hosts processor and network resources. Applications can also leverage offloaded data transfer using application-specific protocols and transport mechanisms to move data between hosts and storage devices.

iSCSI Software Target

An iSCSI software target is integrated into Windows Server 8, and available to leverage for the deployment of iSCSI-based Hyper-V host and virtual machine guest failover clusters. The Windows iSCSI software target provides remote block storage over an Ethernet network. Non-Windows iSCSI initiators are supported, enabling shared storage on Windows servers in heterogeneous environments.

Storage Management

There is a new extensible Windows Storage Management application programming interface (API) in Windows Server 8 that delivers comprehensive access to locally or remotely manage a wide array of storage devices in a uniform manner. Windows Management Instrumentation (WMI) and PowerShell cmdlets are available for programmatic and script-based calls to the API, respectively. The PowerShell cmdlets replace tools like diskpart and diskraid that were used in previous Windows versions.

Conclusion

In this article, you learned about key new storage features in Windows Server 8 that support cloud deployments. In Part 5 of this series, you will learn about cloud storage scenarios that Microsoft supports with Windows Server 8.

If you would like to read the other parts in this article series please go to:

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