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NtfsNTFS or New Technology File System is the standard file system of Windows NT and its descendants Windows 2000, Windows XP and Windows Server 2003. Windows version 95, 98, 98SE and ME, cannot natively read NTFS filesystems, although utilities do exist for this purpose. NTFS replaced Microsoft's previous FAT filesystem, used in MS-DOS and early version of Windows. NTFS has several improvements over FAT such as improved support for metadata and the use of advanced data structures to improve performance, reliability and disk space utilization plus additional extensions such as security access control lists and file system journaling. NTFS has three versions: v1.2 found in NT 3.51 and NT 4, v3.0 found in Windows 2000 and v3.1 found in Windows XP and Windows Server 2003. These versions are sometimes referred to as v4.0, v5.0 and v5.1, after the version of Windows they ship with. Newer versions added extra features: Windows 2000 introduced quotas. Internals In NTFS, everything that has anything to do with a file (file name, creation date, access permissions and even contents) is stored as metadata. This elegant, albeit abstract approach allowed easy addition of filesystem features during the course of Windows NT's development - an interesting example is the addition of fields for indexing used by the Active Directory software. File Names are stored in Unicode (UCS-2.) Internally, NTFS uses B-trees in order to store the file system data; although complex to implement, this allows fast access times and decreases fragmentation. A file system journal is used in order to guarantee the integrity of the file system itself (but not of each individual file). Systems using NTFS are known to have improved reliability, a particularly important requirement considering the unstable nature of the older versions of Windows NT. Details on the implementation's internals are closed, so third-party vendors have a difficult time providing tools to handle NTFS. Currently, the Linux kernel includes a module which makes it possible to read NTFS partitions; however the general complexity of the filesystem and inadequate developer resources, both in time and persons, have delayed the addition of full write support. As a workaround, a project called Captive NTFS allows access to the NTFS by providing the operating system with an interface to the ntfs.sys driver which already exists on most NTFS partitions (and on all Windows NT installations). Though this provides slow read/write support, a few people have reported data loss. Captive NTFS also limits the maximum writable file size on an NTFS partition. Interoperability Microsoft currently provides a tool to convert the FAT32 format to NTFS but not the other way around. PartitionMagic http://www.symantec.com/partitionmagic/index.html by Symantec and the open source NTFSResize utility are both capable of resizing NTFS partitions. For historical reasons, the versions of Windows that do not support NTFS all keep time internally as local zone time, and therefore so do all file systems other than NTFS that are supported by current versions of Windows. However, Windows NT and its descendants keep internal timestamps as GMT/UTC and make the appropriate conversions for display purposes. Therefore, NTFS timestamps are in GMT/UTC. This means that when files are copied or moved between NTFS and non-NTFS partitions, the OS needs to convert timestamps on the fly. But if some files are moved when summer or "daylight" local time is in effect, and other files are moved when winter or "standard" local time is in effect, there can be some ambiguities in the conversions. As a result, especially shortly after one of the days on which local zone time changes, users may observe that some files have timestamps that are incorrect by one hour. See also External links - http://www.winnetmag.com/Windows/Article/ArticleID/15719/15719.html - Inside Win2K NTFS by Mark Russinovich
- http://www.codeproject.com/datetime/dstbugs.asp - Excellent explanation of the timestamp issue with NTFS and seasonal time changes.
- Custer, Helen (1994). Inside the Windows NT File System. Microsoft Press. ISBN 155615660X.
- Nagar, Rajeev (1997). Windows NT File System Internals: A Developer's Guide (1st ed). O'Reilly. ISBN 1565922492.
- Linux-NTFS - an older DEPRECATED (and very unsafe) open source project to add NTFS support to the Linux kernel
- Captive NTFS - A more modern (and much safer) open source programming effort at implementing NTFS support within the Linux kernel
- NTFS.com - documentation and resources for NTFS
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