OPERATING SYSTEMITE2002DIGITAL ASSIGNMENTSUBMITTED BY: PARTHVI SINGHREG. NO.: 20BIT0377WINDOWS OPERATING SYSTEM- FILE SYSTEMThe native file system in Windows is NTFS. It is used for all local volumes. However,associated USB thumb drives, flash memory on cameras, and external disks may be formattedwith the 32-bit FAT file system for portability. FAT is a much older file-system format that isunderstood by many systems besides Windows, such as the software running on cameras. Adisadvantage is that the FAT file system does not restrict file access to authorized users. Theonly solution for securing data with FAT is to run an application to encrypt the data beforestoring it on the file system.In contrast, NTFS uses ACLs to control access to individual files and supports implicitencryption of individual files or entire volumes (using Windows BitLocker feature). NTFSimplements many other features as well, including data recovery, fault tolerance, very largefiles and file systems, multiple data streams, UNICODE names, sparse files, journaling, volumeshadow copies, and file compression.1.NTFS Internal LayoutThe fundamental entity in NTFS is a volume. A volume is created by the Windows logicaldisk management utility and is based on a logical disk partition. A volume may occupy aportion of a disk or an entire disk, or may span several disks.NTFS does not deal with individual sectors of a disk but instead uses clusters as the units ofdisk allocation. A cluster is a number of disk sectors that is a power of 2. The cluster size isconfigured when an NTFS file system is formatted. The default cluster size is based on thevolume size—4 KB forvolumes larger than 2 GB. Given the size of today’s disks, it may make
sense to use cluster sizes larger than the Windows defaults to achieve better performance,although these performance gains will come at the expense of more internal fragmentation.NTFS uses logical cluster numbers (LCNs) as disk addresses. It assigns them by numberingclusters from the beginning of the disk to the end. Using this scheme, the system can calculatea physical disk offset (in bytes) by multiplying the LCN by the cluster size.A file in NTFS is not a simple byte stream as it is in UNIX; rather, it is a structured objectconsisting of typed attributes. Each attribute of a file is an independent byte stream that can becreated, deleted, read, and written. Some attribute types are standard for all files, including thefile name (or names, if the file has aliases, such as an MS-DOS short name), the creation time,and the security descriptor that specifies the access control list. User data are stored in dataattributes.Most traditional data files have an unnamed data attribute that contains all the file’s data.