NTFS first used in the NT operating system,offers the highest level of service and features for Windows computers,and is designed to minimize data loss in an unexpected system outage or hard drive failure. It also includes security features for file servers and personal computers,supports data access control and ownership privileges,that are important for the integrity of critical data. NTFS files and folders can have permissions assigned whether they are shared or not and,is the only file system on Windows that allows you to assign permissions to individual files.
For reliable data storage and data access, NTFS provides file system recovery based on the concept of an atomic transaction. Atomic transactions are a technique for handling modifcations to a database so that system failures do not affect the correctness or integrity of the database. NTFS uses its log file and checkpoint information,to restore the consistency of the file system when the computer is restarted in the event of a system failure. In the event of a bad sector error, NTFS dynamically remaps the cluster containing the bad sector and allocates a new cluster for the data, as well as marking the cluster as bad and no longer using it.
In the event of a system failure, NTFS runs a recovery procedure that accesses information stored in a transaction log file. The NTFS recovery procedure guarantees that the volume is restored to a consistent state. NTFS views each operation that modifies a file on a volume as a transaction and manages each one as an integral unit. After a transaction is started, it is either completed, or if an event occurs that causes the operation to fail, it is rolled back, and the NTFS volume returns to its state before the transaction began.
To ensure that a transaction can either be completed or rolled back, NTFS performs the following steps for each transaction:
Records the metadata operations of a transaction in a log file cached in memory.
Records the actual metadata operations in memory.
Marks the transaction in the cached log file as committed.
Flushes the log file to disk.
Flushes the actual metadata operations to disk.
If a system failure occurs, NTFS then has enough information in the log to complete or abort any partial NTFS transaction. During recovery operations, NTFS redoes each committed transaction found in the log file. Then NTFS locates in the log file the transactions that were not committed at the time of the system failure,and undoes each metadata operation recorded in the log file.
Because NTFS flushes the log to disk before any metadata changes are written to disk, NTFS has complete information available about any metadata changes that need to be rolled back during recovery.
NTFS allows you to set permissions on a file or folder, and specify the groups and users whose access you want to restrict or allow, and then select the type of access.
Data Redundancy and Fault ToleranceIn addition to recoverability of file system data,the NTFS recovery capabilities ensure that the file system on a volume remains accessible, but they make no guarantees for complete recovery of user files. Protection for applications that can not risk losing file data is provided through data redundancy.
NTFS Disk Structure
The structure of NTFS begins with a volume. A volume corresponds to a logical partition on a disk, and it is created when you format a disk or part of a disk for NTFS. You can also create a RAID volume that spans multiple disks.A disk can have one volume or several.During format and setup of a volume file system on a hard disk, a master boot record is created.The master boot record contains a small amount of executable code called the master boot code as well as a partition table for the disk. When a volume is mounted, the master boot record executes the master boot code and transfers control to the boot sector on the disk, allowing the computer to boot the operating system on the file system of that specific volume.
Dependencies on Other Technologies
NTFS depends on the following technologies:
Basic Disks and Volumes
Basic disks and basic volumes are the storage types most often used with Windows operating systems. The term basic disk refers to a disk that contains basic volumes, such as primary partitions and logical drives. The term basic volume refers to a partition on a basic disk.
Dynamic Disks and Volumes
Dynamic disks can use the master boot record or GUID partition table partitioning scheme. All volumes on dynamic disks are known as dynamic volumes. Dynamic disks were first introduced with Windows 2000 and provide features that basic disks do not.
Self Healing NTFS
Before Windows 2008 you had to use the Chkdsk to fix corruptions of NTFS file system volumes on a disk.In Windows Server 2008 you can now use self healing NTFS to protect your entire file system efficiently and reliably.Self healing NTFS attempts to correct corruptions of the NTFS file system online, without requiring Chkdsk.exe to be run.
Self healing NTFS provides the following:
Helps provide continuous availability. The file system is always available, NTFS corrects all detected problems while the system is running.
Preserves data. Self healing NTFS preserves as much data as possible, based on the type of corruption detected. Reduces failed file system mounting requests that occur because of inconsistencies during restart or for an online volume. Self healing NTFS accepts the mount request, but if the volume is known to have some form of corruption, a repair is initiated immediately.
Provides better reporting. Self healing NTFS reports changes made to the volume during repair through existing Chkdsk.exe mechanisms, directory notifications, and update sequence number journal entries.
Allows authorized users to administer and monitor repair operations. Recovers a volume if the boot sector is readable but does not identify an NTFS volume. In this case, the user needs to run an offline tool that repairs the boot sector. Self healing NTFS can then initiate whatever scan is necessary to recover the volume. Validates and preserves data within critical system files.
Improvements in Windows 7 and Windows Server 2008 R2
Several enhancements to improve performance have been made to the NTFS file system in Windows 7 and Windows Server 2008 R2:
T10 Trim delete notification In Windows 7 and Windows Server 2008 R2, for storage devices that support T10 Trim, NTFS now sends a delete notification to the device when files are deleted. This new functionality enables storage devices such as solid state disks (SSDs) to better utilize their storage capability, and it improves their performance.
Oplock semantics Opportunistic locks provide a mechanism that allows file server client computers that are using the SMB and SMB 2.0 protocols to dynamically alter the buffering strategy for a given file or data stream in a consistent manner.
Another change is the introduction of oplock keys, which apply oplocks on a per client, rather than per handle basis.
Support for file system metadata defragmenting Before Windows 7 and Windows Server 2008 R2, certain file system metadata associated with user data files could not be defragmented. Enhancements to the defragment engine enable certain file system metadata to be defragmented.
Improvements to Volume Shrink By optimizing the placement of immovable system files, the ability to shrink a volume through the Volume Shrink utility is improved.
Ability to disable short names on a per volume basis The shortname property 8.3 naming convention can now be individually managed on a per volume basis.The command line utility Fsutil has been enhanced with additional shortname related commands. and can now strip short names from a directory,and keeps a log that contains details of the stripped files and errors that occur.After short names have been stripped, there is no automated way to restore them. If the directory structure has changed in any way, there is no guarantee that the short names will be completely restored.
Improved concurrency of read requests while flushing NTFS now supports a concurrent read request of a file at the same time that cached data is saved to the disk by the flush request.
Native Virtual Hard Disk support
Enhancements to the mount and boot mechanisms and additional support across multiple Windows components provide the following capabilities:
Instance mobility: Migrate an operating system instance from one computer to another without having to reconfigure the operating system, the configured roles, or workloads.
Multiple instance VHD management: Have a single computer maintain multiple instances of operating systems without having to make changes to disk partitioning.
Centralized deployment: Boot from a single, centralized image, significantly easing the deployment and rollout process.
Offline servicing of computer images: Perform offline servicing of a computer by patching the image, rather than having to bring the VHD online to service it.
Backup: Boot from a backup image through Windows Server Backup.
Chkdsk performance improvements In Windows Server 2008 R2, enhancements to the command line tool Chkdsk increase the availability of volumes by reducing the amount of time it takes to perform a Chkdsk run.
Robocopy performance enhancement The copy utility,has been enhanced to allow for multithreaded copies.
Local file copy improvements Optimizations in the memory and cache manager enable improvements in local file copy scenarios. File copy times for small, medium, and large (greater than 8 MB) files have been reduced.