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JFFS2
Journalling Flash File System version 2 or JFFS2 is a log-structured file system for use with flash memory devices. It is the successor to JFFS. JFFS2 has been included into the Linux kernel since September 23, 2001, when it was merged into the Linux kernel mainline as part of the kernel version 2.4.10 release. JFFS2 is also available for a few bootloaders, like Das U-Boot, Open Firmware, the eCos RTOS, the RTEMS RTOS, and the RedBoot. Most prominent usage of the JFFS2 comes from OpenWrt. At least three file systems have been developed as JFFS2 replacements: LogFS, UBIFS, and YAFFS. Features JFFS2 introduced: * Support for NAND flash devices. This involved a considerable amount of work as NAND devices have a sequential I/O interface and cannot be memory-mapped for reading. * Hard links. This was not possible in JFFS because of limitations in the on-disk format. * Compression. Five algorithms are available: zlib, rubin, lzma, rtime, and lzo. * Better performance. JF ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UBIFS
UBIFS (UBI File System, more fully Unsorted Block Image File System) is a flash file system for unmanaged flash memory devices. UBIFS works on top of an UBI (unsorted block image) layer, which is itself on top of a memory technology device (MTD) layer. The file system is developed by Nokia engineers with help of the University of Szeged, Hungary. Development began in earnest in 2007, with the first stable release made to Linux kernel 2.6.27 in October 2008. Two major differences between UBIFS and JFFS2 are that UBIFS supports write caching, and UBIFS errs on the pessimistic side of free space calculation. UBIFS tends to perform better than JFFS2 for large NAND flash memory devices. This is a consequence of the UBIFS design goals: faster mounting, quicker access to large files, and improved write speeds. UBIFS also preserves or improves upon JFFS2's on-the-fly compression, recoverability and power fail tolerance. UBIFS's on-the-fly data compression allows zlib ( deflate alg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of File Systems
The following lists identify, characterize, and link to more thorough information on file systems. Many older operating systems support only their one "native" file system, which does not bear any name apart from the name of the operating system itself. Disk file systems Disk file systems are usually block-oriented. Files in a block-oriented file system are sequences of blocks, often featuring fully random-access read, write, and modify operations. * ADFS – Acorn's Advanced Disc filing system, successor to DFS. * AdvFS – Advanced File System, designed by Digital Equipment Corporation for their Digital UNIX (now Tru64 UNIX) operating system. * APFS – Apple File System is a file system for Apple products. * AthFS – AtheOS File System, a 64-bit journaled filesystem now used by Syllable. Also called AFS. * BFS – the Boot File System used on System V release 4.0 and UnixWare. * BFS – the Be File System used on BeOS, occasionally misnamed as BeFS. Open source impl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LogFS
LogFS is a Linux log-structured and scalable flash file system, intended for use on large devices of flash memory. It is written by Jörn Engel and in part sponsored by the CE Linux Forum. LogFS was introduced in the mainline Linux kernel in version 2.6.34, released on May 16, 2010. It was removed from the codebase during the merge window of version 4.10, in December 2016, because it was "unmaintained for years and seemingly unused". History , LogFS was mature enough to pass its entire test suite, and was subsequently included in the mainline Linux kernel, marked as 'experimental', in version 2.6.34 released on May 16, 2010. However, it did not attract a large user base and was removed from the kernel in December 2016. Operation LogFS was motivated by the difficulties of JFFS2 with larger flash-memory drives. LogFS stores the inode tree on the drive; JFFS2 does not, which requires it to scan the entire drive at mount and cache the entire tree in RAM. For larger drives, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JFFS
The Journaling Flash File System (or JFFS) is a log-structured file system for use on NOR flash memory devices on the Linux operating system. It has been superseded by JFFS2. Design Flash memory (specifically NOR flash) must be erased prior to writing. The erase process has several limitations: * Erasing is very slow (typically 1–100 ms per erase block, which is 103–105 times slower than reading data from the same region). * It is only possible to erase flash in large segments (usually 64 KiB or more), whereas it can be read or written in smaller blocks (often 512 bytes). * Flash memory can only be erased a limited number of times (typically 103–106) before it becomes worn out. These constraints combine to produce a profound asymmetry between patterns of read and write access to flash memory. In contrast, magnetic hard disk drives offer nearly symmetrical read and write access: read speed and write speed are nearly identical (as both are constrained by the rate at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenWrt
OpenWrt (from ''open wireless router'') is an open-source project for embedded operating systems based on Linux kernel, Linux, primarily used on Embedded system, embedded devices to Router (computing), route network traffic. The main components are Linux, util-linux, musl, and BusyBox. All components have been optimized to be small enough to fit into the limited storage and memory available in home routers. OpenWrt is configured using a command-line interface (Almquist shell, ash shell) or a web interface (LuCI). There are about 8000 optional software package (installation), software packages available for installation via the opkg package management system. OpenWrt can run on various types of devices, including Customer-premises equipment, CPE routers, residential gateways, smartphones, pocket computers (e.g., Ben NanoNote). It is also possible to run OpenWrt on personal computers and laptops. History The OpenWrt project was started in 2004 after Linksys had built the firmw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wear Levelling
Wear leveling (also written as wear levelling) is a technique Wear leveling techniques for flash memory systems. for prolonging the service life of some kinds of erasable computer storage media, such as flash memory, which is used in solid-state drives (SSDs) and USB flash drives, and phase-change memory. The idea underpinning wear leveling is similar to changing position of car tires, avoiding repetitive load from being used on the same wheel. Wear leveling algorithms distribute writes more evenly across the entire device, so no block is used more often than others. The term ''preemptive wear leveling'' (PWL) has been used by Western Digital to describe their preservation technique used on hard disk drives (HDDs) designed for storing audio and video data. However, HDDs generally are not wear-leveled devices in the context of this article. Rationale EEPROM and flash memory media have individually erasable segments, each of which can be put through a limited number of erase c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Das U-Boot
Das U-Boot (subtitled "the Universal Boot Loader" and often shortened to U-Boot; see ''#History, History'' for more about the name) is an open-source software, open-source Bootloader, boot loader used in Embedded system, embedded devices to perform various low-level hardware initialization tasks and boot the device's operating system kernel. It is available for a number of computer architectures, including Motorola 68000 series, M68000, ARM architecture, ARM, Blackfin, MicroBlaze, AArch64, MIPS architecture, MIPS, Nios II, SuperH, PowerPC, PPC, Power ISA, RISC-V, LoongArch and x86 architecture, x86. Functionality U-Boot is both a first-stage and second-stage bootloader. It is loaded by the system's ROM (e.g. on-chip ROM of an ARM CPU) from a supported boot device, such as an SD card, SATA drive, NOR flash (e.g. using Serial Peripheral Interface Bus, SPI or I²C), or NAND flash. If there are size constraints, U-Boot may be split into two stages: the platform would load a small ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
YAFFS
YAFFS (Yet Another Flash File System) is a file system designed and written by Charles Manning for the company Aleph One. YAFFS1 was the first version of this file system and was designed for the then-current NAND chips with 512 byte page size (+ 16 byte spare (OOB; Out-Of-Band) area). Work started in 2002, and it was first released later that year. The initial work was sponsored by Toby Churchill Ltd, and Brightstar Engineering. These older chips also generally allow 2 or 3 write cycles per page. YAFFS takes advantage of this: dirty pages are marked by writing to a specific spare area byte. Newer NAND flash chips have larger pages, first 2K pages (+ 64 bytes OOB), later 4K, with stricter write requirements. Each page within an erase block (128 kilobytes) must be written to in sequential order, and each page must be written only once. Designing a storage system that enforces a "write once rule" ("write once property") has several advantages. YAFFS2 was designed to accommodat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NILFS
NILFS or NILFS2 (''New Implementation of a Log-structured File System'') is a log-structured file system implementation for the Linux kernel. It was developed by Nippon Telegraph and Telephone Corporation (NTT) Nippon Telegraph and Telephone Corporation#R.26D laboratories, CyberSpace Laboratories and a community from all over the world. NILFS was released under the terms of the GNU General Public License (GPL). Design "NILFS is a log-structured file system, in that the storage medium is treated like a circular buffer and new blocks are always written to the end.[…]Log-structured file systems are often used for flash media since they will naturally perform wear-leveling;[…]NILFS emphasizes snapshots. The log-structured approach is a specific form of copy-on-write behavior, so it naturally lends itself to the creation of file system snapshots. The NILFS developers talk about the creation of "continuous snapshots" which can be used to recover from user-initiated file system probl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
F2FS
F2FS (Flash-Friendly File System) is a flash file system initially developed by Samsung Electronics for the Linux kernel. The motive for F2FS was to build a file system that, from the start, takes into account the characteristics of NAND flash memory-based storage devices (such as solid-state disks, eMMC, and SD cards), which are widely used in computer systems ranging from mobile devices to servers. F2FS was designed on a basis of a log-structured file system approach, which is adapted to newer forms of storage. Jaegeuk Kim, the principal F2FS author, has stated that it remedies some known issues of the older log-structured file systems, such as the snowball effect of wandering trees and high cleaning overhead. In addition, since a NAND-based storage device shows different characteristics according to its internal geometry or flash memory management scheme (such as the Flash Translation Layer or FTL), it supports various parameters not only for configuring on-disk layo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terabyte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures. To disambiguate arbitrarily sized bytes from the common 8-bit definition, network protocol documents such as the Internet Protocol () refer to an 8-bit byte as an octet. Those bits in an octet are usually counted with numbering from 0 to 7 or 7 to 0 depending on the bit endianness. The size of the byte has historically been hardware-dependent and no definitive standards existed that mandated the size. Sizes from 1 to 48 bits have been used. The six-bit character code was an often-used implementation in early encoding systems, and computers using six-bit and nine-bit bytes were common in the 1960s. These systems often had memory words of 12, 18, 24, 30, 36, 48, or 60 bits, corresponding ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
