It is a long article, some of the key points quoted:
[h=3]Key design changes to help improve availability:[/h]
Online self-healing: The NTFS self-healing feature was introduced in Windows Vista (and in Windows Server 2008) to reduce the need to run chkdsk. Self-healing is a feature built into NTFS that fixes certain classes of corruptions encountered during normal operation, and can make these fixes while still online. If all issues that are detected are self-healed online, there is no need for an offline repair. In Windows 8 we increased the number of issues that can be handled online and hence reduced any further need for chkdsk.
Online verification: Some corruptions are intermittent due to memory issues and may not be a result of an actual corruption on the disk; so we added a new service to Windows 8, called the spot verification service. It is triggered by the file system driver and it verifies that there is actual corruption on the disk before moving the file system along in the health model. This new service runs in the background and does not affect the normal functioning of the system; it does nothing unless the file system driver triggers it to verify a corruption.
Online identification and logging: When an issue is verified, this triggers an online scan of the file system, which runs as a maintenance task in the file system. In Windows 8, scheduled tasks that are for the maintenance of the computer run only when appropriate (during idle time, etc.). This scan can run as a background task while other programs continue to run in the foreground. As the file system is scanned, all issues that are found are logged for later correction.
Precise and rapid correction – At the user or administrator’s convenience, the volume can be taken offline, and the corruptions logged in the previous step can be fixed. The downtime from this operation, called “Spotfix,” takes only seconds, and on Windows Server 8 systems with cluster shared volumes, we’ve eliminated this downtime completely. With this new model, chkdsk offline run time is now directly proportional to the number of corruptions, rather than being proportional to the number of files as in the old model.
[h=4]FAQ[/h] Q) Will the new health model work on removable drives? Yes, this works on removable drives that report fixed media, like most external hard drives. Q) How do I enable the new file system health model? You don’t need to do a thing—the new file system health model is enabled by default. Q) Will the new file system health model apply to Windows Server? Yes, the health model is identical for both server and client. One thing that will be different by default is that the data drives will not be checked or fixed during boot of the system – this maintenance will be left to the administrator when time permits. Q) Can I move between Windows 8 and Windows 7 and not affect the file system health model? Yes, the file system health model will adapt to whichever operating system version it is mounted on. Q) Will ReFS need to run chkdsk? ReFS follows a different model for resiliency and does not need to run the traditional chkdsk utility.
Q) Will I ever need to run the old chkdsk /f? There are cases where failing hardware can produce such severe corruption as to make the file system un-mountable; in these cases, you should perform a full, offline chkdsk to fix the file system. If for some reason this fails, we recommend that you restore from a backup. Q) Is a reboot absolutely required to fix non-system volumes? No, but the Action Center generally provides the simplest experience. If you’re an advanced user, you can fix non-system volumes by opening the properties of the drive, or by running chkdsk \scan <volume>: and chkdsk \spotfix <volume>: from the command line. Q) I run chkdsk /f often to check the status of our drives, is that needed anymore? No, the system will inform you when a corruption is found, and you can then choose to run the chkdsk /scan to detect all the issues. An online chkdsk /scan will not take away from the availability of the drive or system. Q) I run read-only chkdsk today to check the status of our drives; do I still need to do this? No, we recommend you run chkdsk/scan instead, since this will also perform all possible online repairs and will also prepare for a spotfix, if needed.