Published: 02 Apr 2014
The top five Microsoft Windows Server 2012 R2 features include CSV improvements, storage tiers, write-back cache, automatic rebuild of Storage Spaces and data dedupe of VDI workloads.
While some critics dismissed Windows Server 2012 R2 as a minor Windows Server release, the new version incorporates hundreds of new or improved features. In fact, Microsoft's flagship server OS features some very significant enhancements related to storage management.
1. Cluster Shared Volumes improvements
Some of the most beneficial improvements pertaining to storage that Microsoft has made are also the ones that may have received the least publicity. Cluster Shared Volumes (CSVs) is a good example. Microsoft has quietly made some significant changes to improve the resiliency and performance of CSVs.
One such change involves CSV placement. In a failover cluster, the Coordinator Node is considered to be the owner of the CSV. If the Coordinator Node fails, then CSV ownership will be transferred to another node. The problem with this functionality is that in large enterprise environments, a failover cluster may make use of many CSVs. Previously, it was possible for a single node to act as coordinator for most or all the CSVs. If the Coordinator Node were to fail, it could take some time to transfer ownership of all the managed CSVs. In Windows Server 2012 R2, Microsoft has introduced code that evenly balances coordinator responsibilities across the nodes in a cluster so that no single node owns a disproportionate number of CSVs. That helps to make the failover process more efficient.
Cluster nodes also now use multiple instances of the Server service. The Server service coordinates Server Message Block (SMB) communications within the cluster. Having multiple Server service instances allows SMB I/O to continue to function even if there's a problem with the default instance. Along the same lines, Microsoft has also introduced some new diagnostic features that allow you to view the CSV state and availability on a per-node basis. This feature should go a long way toward helping administrators monitor cluster health.
2. Storage tiers
The biggest new storage feature in Windows Server 2012 was arguably Windows Storage Spaces. In Windows Server 2012 R2, Microsoft has done quite a bit of work to improve upon Storage Spaces in an effort to make it more suitable for enterprise customers.
Perhaps the most welcome addition to Windows Storage Spaces is the new storage tiering feature. Windows is able to differentiate between spinning media and solid-state storage within a storage pool. This distinction makes it possible to create virtual hard disks (VHDs) that make use of tiered storage. In doing so, you can specify the amount of traditional storage space and high-performance storage space you wish to include in a VHD.
The storage tier feature offers two main benefits to enterprise users. The first is performance. Frequently read blocks of data (which Microsoft calls hot blocks) are dynamically moved to solid-state storage so they can be accessed as efficiently as possible. The migration of storage blocks between tiers is completely automatic, although it's possible to "pin" a particular file or folder to a specific storage tier as a way of ensuring the resource will always receive a particular level of performance.
The other benefit of the storage tier feature is cost. Windows Storage Spaces has been described by some as a poor man's SAN. Although Storage Spaces are not likely to completely replace SANs any time soon, they do allow administrators to take advantage of SAN-like features (such as storage tiers) using commodity JBOD storage. Even some large enterprises that traditionally use SAN storage have begun to adopt Storage Spaces for use on test or development systems.
Five more storage features in WinServer 2012 R2
With so many noteworthy storage features to choose from, it's difficult to pick the five most important. So, here are five more storage-related features that deserve at least an honorable mention.
Dual parity. The dual parity feature is something that probably should have shown up in Windows Server a long time ago. This feature stores multiple copies of disk parity information so administrators can protect against two simultaneous disk failures.
Server Message Block (SMB) bandwidth management. Windows Server 2012 R2 makes it possible to differentiate between various types of SMB traffic, thereby allowing you to place limits on certain traffic types. Microsoft allows SMB traffic to be classified as default, Live Migration or virtual machine.
iSCSI caching optimization. Previously, the iSCSI Target Server would always bypass the disk cache for all I/O operations. In Windows Server 2012 R2, it doesn't bypass the disk cache unless explicitly requested to do so. The result is better performance.
Parity space support for failover clusters. Parity spaces are now supported for use with failover clusters. In Windows Server 2012, clusters only supported simple and mirrored disks. Windows Server 2012 R2 adds support for single or dual parity.
VHDX files as shared storage. Previously, if you wanted to build a failover cluster that made use of shared storage, the cluster nodes had to be attached to a physical LUN. Now it's possible to build guest clusters that use VHDX-based virtual hard disks as shared storage. These virtual hard disks can be stored in Cluster Shared Volumes or on SMB 3.0 scale-out file shares.
3. Write-back cache
Write-back cache is another notable new feature that goes hand in hand with storage tiers. Whenever a VHD that makes use of tiered storage is created, Windows automatically creates a 1 GB write-back cache on the high-speed tier.
This write-back cache is designed to help improve write performance for the VHD. Because solid-state storage delivers a much higher rate of random write I/O than hard disk drive (HDD) storage, Windows is able to use the write-back cache as a way of smoothing out temporary spikes in write activity. When the inbound I/O activity declines, the data is automatically moved from the cache to the HDD tier.
The write-back cache is automatically created and used on any VHD that uses storage tiers, as long as the high-speed tier is more than 1 GB in size. It's possible to avoid the creation of a write-back cache or to change the cache size, but any changes must be made when the VHD is created (and the VHD must be created through PowerShell). Changes to the cache cannot be made later.
4. Automatic rebuild of Storage Spaces
One of the most interesting new features involves the automatic rebuilding of Storage Spaces after a disk failure. In Windows Server 2012, it was possible to designate a disk within a storage pool to act as a hot spare. That way, if a disk were to fail then the hot spare could take over. Of course, this meant losing some of your storage capacity to a disk that would only be used in emergency situations.
In Windows Server 2012 R2, hot spares are no longer needed. If a physical disk fails, the disk contents can be written to multiple physical disks within the storage pool, rather than just written to a dedicated hot spare. An added benefit is that disk rebuild times tend to be faster because multiple disks are involved in the process.
5. Data deduplication of virtual desktop infrastructure (VDI) workloads
In Windows Server 2012, Microsoft introduced a new data deduplication feature for NTFS volumes. Curiously, Microsoft placed numerous restrictions on the use of this feature. For instance, deduplication wasn't supported for the new ReFS file system, and it couldn't be used on volumes containing virtual machine components.
With Windows Server 2012 R2, Microsoft has slightly eased the restriction pertaining to the use of native deduplication and virtual machines. While native deduplication is still not supported for use on volumes containing virtual server components, Microsoft now supports the deduplication of volumes containing VDI workloads.
Using deduplication in VDI environments can result in a tremendous space savings since virtual desktops tend to have a lot of redundancy from one VM to the next. In fact, deduplicating volumes containing VDI components can result in such significant space savings that some organizations have found that they're able to store deduplicated virtual desktops on SSD storage, which vastly improves VDI performance.
R2 delivers key storage functionality
Windows Server 2012 R2 offers numerous storage improvements. Many of the new storage features build on features that were introduced in Windows Server 2012, such as Storage Spaces. Although Windows Servers are not yet a full-blown SAN alternative, Windows Server 2012 R2 features a number of storage enhancements that were previously only available at the hardware level.
About the author:
Brien Posey is a Microsoft MVP with two decades of IT experience. Previously, Brien was CIO for a national chain of hospitals and health care facilities.
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