Windows Server 2012

Windows Server 2012, codenamed "Windows Server 8", is the sixth release of Windows Server. It is the server version of Windows 8 and succeeds Windows Server 2008 R2. Two pre-release versions, a developer preview and a beta version, were released during development. The software was generally available to customers starting on September 4, 2012.

Unlike its predecessor, Windows Server 2012 has no support for Itanium-based computers, and has four editions. Various features were added or improved over Windows Server 2008 R2 (with many placing an emphasis on cloud computing), such as an updated version of Hyper-V, an IP address management role, a new version of Windows Task Manager, and ReFS, a new file system. Windows Server 2012 received generally good reviews in spite of having included the same controversial Metro-based user interface seen in Windows 8.

History
Windows Server 2012, codenamed "Windows Server 8", is the sixth release of Windows Server family of operating systems developed concurrently with Windows 8. It was not until 17 April 2012 that the company announced that the final product name would be "Windows Server 2012".

Microsoft introduced Windows Server 2012 and its developer preview in the BUILD 2011 conference on 9 September 2011. However, unlike Windows 8, the developer preview of Windows Server 2012 was only made available to MSDN subscribers. It included a graphical user interface (GUI) based on Metro design language and a new Server Manager, a graphical application used for server management. On 16 February 2012, Microsoft released an update for developer preview build that extended its expiry date from 8 April 2012 to 15 January 2013.

Before Windows Server 2012 was finalized, two test builds were made public. A public beta version of Windows Server 2012 was released along with the Windows 8 Consumer Preview on 29 February 2012. The release candidate of Windows Server 2012 was released on 31 May 2012, along with the Windows 8 Release Preview.

The product was released to manufacturing on 1 August 2012 and became generally available on 4 September 2012. However, not all editions of Windows Server 2012 were released at the same time. Windows Server 2012 Essentials was released to manufacturing on 9 October 2012 and was made generally available on 1 November 2012. As of 23 September 2012, all students subscribed to DreamSpark program can download Windows Server 2012 Standard or Datacenter free of charge.

Installation options
Unlike its predecessor, Windows Server 2012 can switch between "Server Core" and "Server with a GUI" installation options without a full reinstallation. Server Core - an option with a command-line interface only - is now the recommended configuration. There is also a third installation option that allows some GUI elements such as MMC and Server Manager to run, but without the normal desktop, shell or default programs like File Explorer.

User interface
Server Manager has been redesigned with an emphasis on easing management of multiple servers. The operating system, like Windows 8, uses the Metro-based user interface unless installed in Server Core mode. Windows Store is available in this version of Windows but is not installed by default. Windows PowerShell in this version has over 2300 commandlets, compared to around 200 in Windows Server 2008 R2.

Task Manager
Windows Server 2012 includes a new version of Windows Task Manager together with the old version. In the new version the tabs are hidden by default showing applications only. In the new Processes tab, the processes are displayed in varying shades of yellow, with darker shades representing heavier resource use. It lists application names and status, as well as CPU, memory, hard disk and network utilization. The process information found in the older versions are now moved to the new Details tab. The Performance tab shows "CPU", "Memory", "Disk", "Wi-Fi" and "Ethernet" graphs. The CPU tab no longer displays individual graphs for every logical processor on the system by default; instead, it can display data for each NUMA node. When displaying data for each logical processor for machines with more than 64 logical processors, the CPU tab now displays simple utilization percentages on heat-mapping tiles. The color used for these heat maps is blue, with darker shades again indicating heavier utilization. Hovering the cursor over any logical processor's data now shows the NUMA node of that processor and its ID, if applicable. Additionally, a new Startup tab has been added that lists startup applications, however this tab does not exist in Windows Server 2012. The new task manager recognizes when a Windows Store app has the "Suspended" status.

IP address management (IPAM)
Windows Server 2012 has an IP address management role for discovering, monitoring, auditing, and managing the IP address space used on a corporate network. The IPAM is used for the management and monitoring of Domain Name System (DNS) and Dynamic Host Configuration Protocol (DHCP) servers. Both IPv4 and IPv6 are fully supported.

Active Directory
Windows Server 2012 has a number of changes to Active Directory from the version shipped with Windows Server 2008 R2. The Active Directory Domain Services installation wizard has been replaced by a new section in Server Manager, and a GUI has been added to the Active Directory Recycle Bin. Multiple password policies can be set in the same domain. Active Directory in Windows Server 2012 is now aware of any changes resulting from virtualization, and virtualized domain controllers can be safely cloned. Upgrades of the domain functional level to Windows Server 2012 are simplified; it can be performed entirely in Server Manager. Active Directory Federation Services is no longer required to be downloaded when installed as a role, and claims which can be used by the Active Directory Federation Services have been introduced into the Kerberos token. Windows Powershell commands used by Active Directory Administrative Center can be viewed in a "Powershell History Viewer".

Hyper-V
Windows Server 2012, along with Windows 8, includes a new version of Hyper-V, as presented at the Microsoft BUILD event. Many new features have been added to Hyper-V, including network virtualization, multi-tenancy, storage resource pools, cross-premise connectivity, and cloud backup. Additionally, many of the former restrictions on resource consumption have been greatly lifted. Each virtual machine in this version of Hyper-V can access up to 64 virtual processors, up to 1 terabyte of memory, and up to 64 terabytes of virtual disk space per virtual hard disk (using a new .vhdx format). Up to 1024 virtual machines can be active per host, and up to 8000 can be active per failover cluster. SLAT is a required processor feature for Hyper-V on Windows 8, while for Windows Server 2012 it is only required for the supplementary RemoteFX role.

ReFS
Resilient File System (ReFS), codenamed "Protogon", is a new file system in Windows Server 2012 initially intended for file servers that improves on NTFS in some respects. Major new features of ReFS include:


 * Improved reliability for on-disk structures: ReFS uses B+ trees for all on-disk structures including metadata and file data. Metadata and file data are organized into tables similar to a relational database. The file size, number of files in a folder, total volume size and number of folders in a volume are limited by 64-bit numbers; as a result ReFS supports a maximum file size of 16 Exabytes, a maximum of 18.4 × 1018 folders and a maximum volume size of 1 Yottabyte (with 64 KB clusters) which allows large scalability with no practical limits on file and folder size (hardware restrictions still apply). Free space is counted by a hierarchical allocator which includes three separate tables for large, medium, and small chunks. File names and file paths are each limited to a 32 KB Unicode text string.
 * Built-in resilience: ReFS employs an allocation-on-write update strategy for metadata, which allocates new chunks for every update transaction and uses large IO batches. All ReFS metadata has built-in 64-bit checksums which are stored independently. The file data can have an optional checksum in a separate "integrity stream", in which case the file update strategy also implements allocation-on-write; this is controlled by a new "integrity" attribute applicable to both files and directories. If nevertheless file data or metadata becomes corrupt, the file can be deleted without taking down the whole volume offline for maintenance, then restored from the backup. As a result of built-in resiliency, administrators do not need to periodically run error-checking tools such as CHKDSK when using ReFS.
 * Compatibility with existing APIs and technologies: ReFS does not require new system APIs and most file system filters continue to work with ReFS volumes. ReFS supports many existing Windows and NTFS features such as BitLocker encryption, Access Control Lists, USN Journal, change notifications, symbolic links, junction points, mount points, reparse points, volume snapshots, file IDs, and oplock. ReFS seamlessly integrates with Storage Spaces, a storage virtualization layer that allows data mirroring and striping, as well as sharing storage pools between machines. ReFS resiliency features enhance the mirroring feature provided by Storage Spaces and can detect whether any mirrored copies of files become corrupt using background data scrubbing process, which periodically reads all mirror copies and verifies their checksums then replaces bad copies with good ones.

Some NTFS features are not supported in ReFS, including named streams, object IDs, short names, file compression, file level encryption (EFS), user data transactions, hard links, extended attributes, and disk quotas. Sparse files was not supported by Preview, but it is supported by RTM. ReFS does not itself offer data deduplication. Dynamic disks with mirrored or striped volumes are replaced with mirrored or striped storage pools provided by Storage Spaces. However, in Windows Server 2012, automated error-correction is only supported on mirrored spaces, and booting from ReFS is not supported either.

IIS 8.0
Windows Server 2012 includes version 8.0 of Internet Information Services (IIS). The new version contains new features such as SNI, CPU usage caps for particular websites, centralized management of SSL certificates, WebSocket support and improved support for NUMA, but few other substantial changes were made.

Scalability
Windows Server 2012 supports the following maximum hardware specifications. Windows Server 2012 improves over its predecessor Windows Server 2008 R2:

System requirements
Windows Server 2012 runs only on x64 processors. Unlike its predecessor, Windows Server 2012 does not support Itanium.

Upgrades from Windows Server 2008 and Windows Server 2008 R2 are supported, although upgrades from prior releases are not.

Editions
Windows Server 2012 has four editions: Foundation, Essentials, Standard and Datacenter.

Reception
Reviews of Windows Server 2012 have been generally positive. Simon Bisson of ZDnet described it as "ready for the datacenter, today," while Tim Anderson of The Register said that "The move towards greater modularity, stronger automation and improved virtualisation makes perfect sense in a world of public and private clouds" but remarked that "That said, the capability of Windows to deliver obscure and time-consuming errors is unchanged" and concluded that "Nevertheless, this is a strong upgrade overall." InfoWorld noted that Windows Server 2012 has the Metro UI, which had led to mixed reviews for Windows 8, but mentioned that "Microsoft is pushing harder for a GUI-less install than a Metro-based screen", with reference to the improved Server Core installation option and the improvements for Windows PowerShell. However, Michael Otey of Windows IT Pro expressed dislike with the new Metro interface and the lack of ability to use the older desktop interface alone, saying that most users of Windows Server manage their servers using the graphical user interface rather than PowerShell. The Australian construction company Kennards found the OS stable.

Paul Ferrill wrote that "Windows Server 2012 Essentials provides all the pieces necessary to provide centralized file storage, client backups, and remote access," but Tim Anderson contended that "Many businesses that are using SBS2011 and earlier will want to stick with what they have", citing the absence of Exchange, the lack of ability to synchronize with Active Directory Federation Services and the 25-user limit, while Paul Thurott wrote "you should choose Foundation only if you have at least some in-company IT staff and/or are comfortable outsourcing management to a Microsoft partner or solution provider" and "Essentials is, in my mind, ideal for any modern startup of just a few people."

Windows Server 2012 R2
The current version Windows Server 2012 R2 was released on October 18, 2013. It was unveiled on June 3, 2013 at TechEd North America. According to Windows Server 2012 R2 datasheet published on May 31, 2013, there are three editions of this operating system: Essentials, Standard and Datacenter. As with Windows Server 2012, the Datacenter and Standard editions are feature identical, varying only based on licensing (particularly licensing of Hyper-V VMs). The Essentials edition has the same features as the Datacenter and Standard products, with some restrictions.

Changes from Windows Server 2012
Microsoft has confirmed the following changes introduced by Windows Server 2012 R2:
 * Automated Tiering: Storage Spaces stores most frequently accessed files on fastest physical media
 * Deduplication for VHD: Reduces the storage space for VHD files with largely similar contents by storing the similar contents only once
 * Windows PowerShell v4, which now includes a Desired State Configuration (DSC) feature
 * Integrated Office 365 support (Essentials edition)
 * Return of the Windows Start button
 * UEFI-based virtual machines
 * Upgrades from driver emulators to synthetic hardware drivers to minimize legacy support
 * Faster VM deployment (approximately half the time)
 * Internet Information Services 8.5: Support for logging to Event Tracing for Windows and the ability to log any request/response headers. To improve scalability, if IIS is configured with 100 or more web sites, by default it will not automatically start any of them. Alongside this, a new "Idle Worker Process Page-Out" configuration option has been added to application pools to instruct Windows to page-out the process if it has been idle for the idle time-out period (by default, 20 minutes).
 * Server Message Block: Performance and event logging quality improvements, support for Hyper-V Live Migration over SMB, bandwidth prioritization management, and the ability to remove SMB 1.0 support
 * Windows Deployment Services: Support for managing WDS via PowerShell.
 * Windows Defender is available in a Server Core installation, and is installed and enabled by default.
 * IP Address Management (IPAM): Extended to support role-based access control, allowing for fine-grained control over which users can view or change configurations for DHCP reservations, scopes, IP address blocks, DNS resource records, etc. Additionally, IPAM can integrate with System Center Virtual Machine Manager 2012 R2 to have coordinated IP policy across both physical and virtual environments. The IPAM database can be stored in a SQL Server instance instead of Windows Internal Database.
 * Group Policy has a new "Policy Cache" setting which allows domain-joined machines to store a copy of the group policy settings on the client machine and, depending on the speed of access to the domain controller, use those at startup time instead of waiting for the policy settings to download. This can improve startup times on machines that are disconnected from the company network. New Group Policy settings have been added to cover new features in Windows 8.1 and Internet Explorer 11, such as enabling/disabling SPDY/3 support, configuring start screen layouts, and detecting phone numbers in web pages.
 * TLS support is extended to support RFC 5077, "Transport Layer Security (TLS) Session Resumption without Server-Side State", which improves performance of long-running TLS-secured connections that need to reconnect due to session expiration.