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26-398: Fast File System may refer to: Berkeley Fast File System , as used by the various BSD variants Amiga Fast File System , as used by AmigaOS Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Fast File System . If an internal link led you here, you may wish to change

52-401: A fully optimized system, the head could be moved between close tracks to read scattered sectors from alternating tracks while waiting for the platter to spin around. As disks grew larger and larger, sector-level optimization became obsolete (especially with disks that used linear sector numbering and variable sectors per track). With larger disks and larger files, fragmented reads became more of

78-707: A mechanism that maintains the file system consistency without limiting the performance in the way the traditional sync mode did. This has the side effect of reducing the requirement of file system checking after a crash or power failure. To overcome the remaining issues after a failure, a background fsck utility was introduced. In UFS2, Kirk McKusick and Poul-Henning Kamp extended the FreeBSD FFS and UFS layers to add 64-bit block pointers (allowing volumes to grow up to 8 zebibytes ), variable-sized blocks (similar to extents ), extended flag fields, additional 'birthtime' stamps, extended attribute support and POSIX1.e ACLs. UFS2 became

104-461: A problem. To combat this, BSD originally increased the filesystem block size from one sector to 1 K in 4.0 BSD; and, in FFS, increased the filesystem block size from 1 K to 8 K. This has several effects. The chance of a file's sectors being contiguous is much greater. The amount of overhead to list the file's blocks is reduced, while the number of bytes representable by any given number of blocks

130-565: A single "fragment" block instead of multiple mostly empty blocks. The work on Berkeley FFS was widely adopted by other Unix vendors, and the family of filesystems derived from it are collectively known as UFS. Vendors of some proprietary Unix systems, such as SunOS / Solaris , System V Release 4 , HP-UX , and Tru64 UNIX , and open Unix derived systems like illumos , have adopted UFS. Most of them adapted UFS to their own uses, adding proprietary extensions that may not be recognized by other vendors' versions of Unix. Many have continued to use

156-455: A single shared tail block. While this may, at first, seem like it would significantly increase file system fragmentation, the negative effect can be mitigated with readahead features on modern operating systems – when dealing with short files, several tails may be close enough to each another to be read together, and thus a disk seek is not introduced. Such file systems often employ heuristics in order to determine whether tail packing

182-409: A tail block in some way to allow it to store fragments from other files. Some block suballocation schemes can perform allocation at the byte level; most, however, simply divide up the block into smaller ones (the divisor usually being some power of 2). For example, if a 38 KiB file is to be stored in a file system using 32 KiB blocks, the file would normally span two blocks, or 64 KiB, for storage;

208-542: A version of UFS. In Apple 's Mac OS X , it was available as an alternative to HFS+ , their proprietary filesystem. However, as of Mac OS X Leopard , it was no longer possible to install Mac OS X on a UFS-formatted volume. In addition, one cannot upgrade older versions of Mac OS X installed on UFS-formatted volumes to Leopard; upgrading requires reformatting the startup volume. There was a 4 GB file limit for disks formatted as UFS in Mac OS X. As of Mac OS X Lion , UFS support

234-596: Is called "UFS", and the lower layers are called "FFS" and "LFS". In some of those systems, the term "FFS" is used for the combination of the FFS lower layer and the UFS upper layer, and the term "LFS" is used for the combination of the LFS lower layer and the UFS upper layer. Kirk McKusick implemented block reallocation, a technique that reorders the blocks in the file system just before the writes are done to reduce fragmentation and control file system aging. He also implemented soft updates ,

260-494: Is commonly done by packing the "tail", or last partial block, of multiple files into a single block. File systems have traditionally divided the disk into equally sized blocks to simplify their design and limit the worst-case fragmentation . Block sizes are typically multiples of 512 bytes due to the size of hard disk sectors . When files are allocated by some traditional file systems, only whole blocks can be allocated to individual files. But as file sizes are often not multiples of

286-456: Is increased. Larger disk sizes are also possible, since the maximum number of blocks is limited by a fixed bit-width block number. However, with larger block sizes, disks with many small files will waste space, since each file must occupy at least one block. Because of this, BSD added block-level fragmentation , also called block suballocation, tail merging, or tail packing , where the last partial block of data from several files may be stored in

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312-425: Is no standard implementation for the vendor extensions to UFS, Linux does not have full support for writing to UFS. The native Linux ext2 filesystem was inspired by UFS1 but does not support fragments and there are no plans to implement soft updates. (In some 4.4BSD-derived systems, the UFS layer can use an ext2 layer as a container layer, just as it can use FFS and LFS.) NeXTStep , which was BSD-derived, also used

338-648: Is worthwhile in a given situation, and defragmentation software may use a more evolved heuristic. In some scenarios where the majority of files are shorter than half the block size, such as in a folder of small source code files or small bitmap images, tail packing can increase storage efficiency even more than twofold, compared to file systems without tail packing. This not only translates into conservation of disk space, but may also introduce performance increases, as due to higher locality of reference , less data has to be read, also translating into higher page cache efficiency. However, these advantages can be negated by

364-451: The data blocks they referred to caused thrashing . Marshall Kirk McKusick , then a Berkeley graduate student, optimized the V7 FS layout to create BSD 4.2 's FFS (Fast File System) by inventing cylinder groups, which break the disk up into smaller chunks, with each group having its own inodes and data blocks. The intent of BSD FFS is to try to localize associated data blocks and metadata in

390-575: The file system block size, this design inherently results in the last blocks of files (called tails ) occupying only a part of the block, resulting in what is called internal fragmentation (not to be confused with external fragmentation ). This waste of space can be significant if the file system stores many small files and can become critical when attempting to use higher block sizes to improve performance. UFS and other derived UNIX file systems support fragments which greatly mitigate this effect. Block suballocation addresses this problem by dividing up

416-406: The following parts: Inodes are numbered sequentially, starting at 0. Inode 0 is reserved for unallocated directory entries, inode 1 was the inode of the bad block file in historical UNIX versions, followed by the inode for the root directory , which is always inode 2 and the inode for the lost+found directory which is inode 3. Directory files contain only the list of filenames in the directory and

442-451: The implementation of UFS1 and UFS2 is split into two layers: an upper layer that provides the directory structure and supports metadata (permissions, ownership, etc.) in the inode structure, and lower layers that provide data containers implemented as inodes. This was done to support both the traditional FFS and the LFS log-structured file system with shared code for common functions. The upper layer

468-407: The inode associated with each file. All file metadata are kept in the inode. Early Unix filesystems were referred to simply as FS . FS only included the boot block, superblock, a clump of inodes , and the data blocks. This worked well for the small disks early Unixes were designed for, but as technology advanced and disks grew larger, moving the head back and forth between the clump of inodes and

494-410: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Fast_File_System&oldid=932822616 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Berkeley Fast File System A UFS volume is composed of

520-488: The need for background fsck, and NFSv4 ACLs. FreeBSD, NetBSD, OpenBSD, and DragonFly BSD also include the Dirhash system, developed by Ian Dowse. This system maintains an in-memory hash table to speed up directory lookups. Dirhash alleviates a number of performance problems associated with large directories in UFS. Linux includes a UFS implementation for binary compatibility at the read level with other Unixes, but since there

546-575: The original block size and data field widths as the original UFS, so some degree of read compatibility remains across platforms. Compatibility between implementations as a whole is spotty at best. As of Solaris 7 , Sun Microsystems included UFS Logging, which brought filesystem journaling to UFS, which is still available in current versions of Solaris and illumos. Solaris UFS also has extensions for large files and large disks and other features. In 4.4BSD and BSD Unix systems derived from it, such as FreeBSD , NetBSD , OpenBSD , and DragonFlyBSD ,

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572-404: The remaining 26 KiB of the second block becomes unused slack space. With an 8 KiB block suballocation, however, the file would occupy just 6 KiB of the second block, leave 2 KiB (of the 8 KiB suballocation block) slack and free the other 24 KiB of the block for other files. Some file systems have since been designed to take advantage of this unused space, and can pack the tails of several files in

598-421: The same cylinder group and, ideally, all of the contents of a directory (both data and metadata for all the files) in the same or nearby cylinder group, thus reducing fragmentation caused by scattering a directory's contents over a whole disk. Some of the performance parameters in the superblock included number of tracks and sectors, disk rotation speed, head speed, and alignment of the sectors between tracks. In

624-454: The supported UFS version starting with FreeBSD 5.0. FreeBSD also introduced soft updates and the ability to make file system snapshots for both UFS1 and UFS2. These have since been ported to NetBSD, but eventually soft updates (called soft dependencies in NetBSD) was removed from NetBSD 6.0 in favor of the less complex file system journaling mechanism called WAPBL (also referred as logging), which

650-493: Was added to FFS in NetBSD 5.0. OpenBSD has supported soft updates since version 2.9 and has had UFS2 (FFS2) support (no ACLs) since version 4.2. OpenBSD has now made UFS2 the default UFS version and will be included with the 6.7 release. Since FreeBSD 7.0, UFS also supports filesystem journaling using the gjournal GEOM provider. FreeBSD 9.0 adds support for lightweight journaling on top of soft updates (SU+J), which greatly reduces

676-451: Was completely dropped. Block suballocation Block suballocation is a feature of some computer file systems which allows large blocks or allocation units to be used while making efficient use of empty space at the end of large files, space which would otherwise be lost for other use to internal fragmentation . In file systems that don't support fragments, this feature is also called tail merging or tail packing because it

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