- You can perform live migrations of virtual machines from Windows Server 2012 hosts to Windows Server 2012 R2 hosts and vice versa, despite the difference in versions, which means zero downtime.
In Windows Server 2012 R2, the PowerShell command-line scripting language introduces a feature called Desired State Configuration, or DSC. It uses a declarative syntax to define a configuration for a server and then uses PowerShell remoting to apply that desired configuration to a group of servers all at once.
This automated configuration approach goes even further to attempt some repairs when configurations of individual servers drift from the original target. This is great for large farms of servers that all need to be identically configured. Without installing a management layer or other agents, you can initially deploy and then maintain the configuration of a platform of servers right from the command line, all with some easy scripting.
One of the unheralded improvements in Windows Server 2012 was deduplication technology, which is essentially an algorithm that detects identical data on a drive and removes all but one copy of it to save space. It works very well and can result in real savings on your storage costs.
Windows Server 2012 R2 takes that one step further and now allows for deduplication of open VHD/VHDX files -- essentially, running virtual machines and virtual hard disk files. In addition to saving valuable space on hypervisors, deduplicated VMs actually boot faster than non-deduplicated machines booting off the same storage hardware and host. This is mainly because of caching in memory that is done with the initial re-pairing of deduplicated data with the un-deduplicated chunks.
With the new release, deduplication now works on VMs and virtual files that are open and running.
With deduplication in 2012 R2 enabled, my tests showed, you can gain space savings as high as 90% on VDI deployments with minimal impact on performance -- and in some cases (like booting) even realize an increase in performance. That is pretty impressive.
The R2 release also expands Storage Spaces, the feature introduced in Windows Server 2012 that allows large boxes of cheap, regular disks to scale inexpensively when compared to dedicated storage area network configurations. In R2, Storage Spaces can actively manage solid-state disks as members of a storage pool and tier frequently used documents and files on the SSDs for super-fast access. This happens while moving "colder," less frequently used files to cheaper spinning media.
The advantage is this lets you get much faster access to the most popular files, still using standard SSDs and HDDs, without having to invest in SANs costing tens or hundreds of thousands of dollars. You can let Windows detect which files are most frequently used, or you as the administrator can "pin" certain files to the hot SSD tier to ensure they will always be present.
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