This article describes several design changes introduced with Windows 8 which change the supported boot configurations for users which utilize multiple operating systems on their personal computer, or for users which physically move storage devices with NTFS volumes between Windows 8 and a prior version of Windows.
As detailed in the Building Windows 8 blog, Windows 8 introduced much faster boot times as a result of the introduction of “Hybrid Boot”. With the new model, Windows 8 will log off active users, but instead of terminating the kernel session, the system is hibernated. This means that the memory state of running system processes, devices, and file systems are saved to the Hiberfile instead of being dismounted and shutdown. On resume, the Hiberfile is read which resumes the memory state, drivers are initialized, and the user session is prepared. By not having to perform a full boot, the time necessary to start your system dramatically decreases.
Also with Windows 8, there has been work done in the NT File System (NTFS) to reduce the I/O count of log file writes. NTFS uses a log file to record changes to file system metadata before they are actually applied and persisted to disk – this is the basic principle of write-ahead logging. This method helps ensure consistency of on-disk metadata structures in the event of an unexpected unclean dismount (for example caused by a power interruption). In order to reduce the I/O count of log file writes, it was necessary to change the way records are written, and as a result, there was a format change and version number was incremented from version 1.1 to 2.0.
While these two changes are fundamentally designed to work together to deliver better performance, there are inherent dependencies on Windows 8 that can result in incompatibilities with systems with multiple versions of Windows installed in certain configurations and boot scenarios, or for users which physically move NTFS volumes between Windows 8 and a prior version of Windows. Additional Background As discussed in the prior section, a change was made to the NTFS Log File structure in Windows 8 to reduce I/O counts, improving system performance, and with potentially reduced power consumption. However, a side effect of this change is that the new log format is unrecognizable with prior versions of Windows, which may result in a prior version of NTFS marking the volume as corrupt (since the contents of the log is in an unrecognized format). This will trigger a chkdsk run upon reboot to ensure that file system metadata is consistent, which will clear the corrupted state of the log file and return the file system to a clean state.
To help prevent prior versions of Windows mounting a NTFS volume with the new log file version, we’ve added logic to the NTFS driver in Windows 8 which does the following:
NOTE: Most USB Flash keys or Flash Media Cards with a caching policy set to “Optimize for Quick Removal” will not be upgraded to the new log structure and version number and do not have the potential for down-level incompatibility. These devices typically report themselves as “Removable Media” and “Hot-Pluggable”.
When a system with multiple versions of Windows installed is resumed from a Hybrid Boot state, the boot process will fully restore Windows 8 and remount previously active volumes before providing a selection screen to choose another version to boot. If the user selects an alternate version, the system is rebooted (which allows for active file systems to dismount and in turn downgrade the log file structure and version to one that is compatible with all prior versions of Windows) and the system will load the desired version. In most scenarios, this will not result in a previous version of Windows mounting a NTFS volume with an unrecognized log file structure and version number.
However, as part of the design of Hybrid Boot, the Windows 8 kernel is not fully shutdown unless a restart is requested, thus any mounted file systems do not have an opportunity to dismount when the machine is Hibernated. As a result, active file systems will not be down-graded to the compatible log version 1.1 after the Hibernate. Thus, removing a physical drive containing active file systems from a Windows 8 machine after the system is Hibernated, and connecting that drive to a prior version of Windows will result in the volume being marked as corrupted. A full chkdsk run will be required to clear the corrupted state of the volume, which will return it to a healthy state.
If you anticipate that you will be physically moving storage devices with a caching policy set to “Optimize for Performance”, or storage devices attached through SATA or SAS between Windows 8 and a prior version of Windows, it is recommended that you either disable Hybrid Boot, or to set a registry key to prevent NTFS from upgrading the Logfile structure and version number to 2.0 upon mount. Details on how either of these procedures, how you can determine if your volume has been upgraded to the new Logfile structure, and how to determine your storage device’s caching policy follows in this article. Supported Multi-OS Boot Configurations As Hybrid Boot introduces a fundamental change to the way Windows 8 is started, the following details the supported configurations for booting Windows 8:
Resolution Summary
Detailed Resolution Steps
Important! This section, method, or task contains steps that can potentially change key file system behavior. Therefore, make sure that you follow these steps carefully.
Note: These steps are only applicable to systems running Windows 8 or Windows Server 2012.
Checking the Logfile version Number
Important! This section, method, or task contains steps that can potentially change key system behavior and settings. Therefore, make sure that you follow these steps carefully.
To disable Windows Hybrid Boot, and to have your system perform a full shutdown upon either pressing the Power Button or clicking the “Shutdown” option in the Charms bar, please follow the below steps.
Note: These steps are only applicable to systems running Windows 8.
Important! This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
To turn off the behavior of NTFS upgrading the log file structure and version number to 2.0 upon a mount of a NTFS volume in Windows 8, please follow the below steps. Note that this registry key does not persist the upgrade behavior to the volume, it only changes the behavior of the NTFS driver on the local system.