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隨著信息技術的不斷發(fā)展，數(shù)據(jù)存儲與處理已經(jīng)成為了企業(yè)發(fā)展過程中重要的一環(huán)。而作為存儲技術的基礎之一，存儲介質的發(fā)展越來越由硬件向軟件方向發(fā)展。在這個背景下，Linux FTL通用設備層（FTL，F(xiàn)lash Translation Layer）的應用與優(yōu)勢越來越被人們關注。
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一、Linux FTL通用設備層的概念與發(fā)展
在之前的存儲介質中，例如磁盤，它們使用的是磁盤調度算法，通過分為循環(huán)隊列等方式進行數(shù)據(jù)的管理。而在存儲介質逐漸由磁盤向Flash發(fā)展過程中，由于Flash芯片的讀寫速度很快，因此采用了FTL技術。
FTL技術的產(chǎn)生主要是基于Flash芯片的特性，他本身是不支持隨意改變已經(jīng)存儲的數(shù)據(jù)，也就是常說的“只能寫不能改”，因此必須要有一種將新數(shù)據(jù)轉化成Flash芯片可識別的方式，而FTL便是實現(xiàn)這一過程的一種技術手段。
而隨著Linux操作系統(tǒng)的不斷成長，章文嵩先生在加拿大滑鐵盧大學于2023年發(fā)表“通用Linux Flash Translation Layer”，它是一種硬件抽象層，為文件系統(tǒng)層提供與Flash存儲介質的通信，并進行數(shù)據(jù)塊的管理和映射。
二、Linux FTL通用設備層的應用
FTL技術已經(jīng)廣泛應用于各種Flash存儲介質中，例如USB存儲設備、固態(tài)硬盤、以及現(xiàn)在越來越流行的移動設備等，而Linux FTL通用設備層的應用范圍也不斷擴大。
1.移動設備
在移動設備中，Linux FTL通用設備層技術不斷優(yōu)化將Flash儲存技術用在移動設備中，其可靠性和性能都得到了很好的提升。尤其是在安卓操作系統(tǒng)中，Linux FTL通用設備層技術已經(jīng)得到廣泛應用，并為人們帶來了更加先進的移動設備體驗。
2.車載娛樂系統(tǒng)
Linux FTL通用設備層技術也被廣泛應用于車載娛樂系統(tǒng)中。在這個系統(tǒng)中，大量的集成電路、嵌入式Linux操作系統(tǒng)和人機交互技術被運用，以實現(xiàn)音頻、視頻、導航等功能。
3.工業(yè)控制
在工業(yè)控制領域，Linux FTL通用設備層技術也被廣泛應用。在控制過程中，工控機的存儲器對于特定控制器內的代碼和數(shù)據(jù)至關重要，而Linux FTL通用設備層技術可有效保證這些數(shù)據(jù)的讀寫效率和穩(wěn)定性。
三、Linux FTL通用設備層的優(yōu)勢
Linux FTL通用設備層技術具有以下優(yōu)勢：
1.良好的可擴展性
Linux FTL通用設備層技術通過模塊化的設計思路，允許用戶根據(jù)自身需要自由拓展功能。用戶可以將支持不同的Flash芯片的模塊添加到系統(tǒng)中，從而實現(xiàn)通用性。
2.良好的穩(wěn)定性
FTL技術的主要作用是在文件系統(tǒng)和硬盤之間進行數(shù)據(jù)翻譯，保證數(shù)據(jù)正常傳輸且不被破壞，因此穩(wěn)定性是必須的。而FTL技術在保證其高性能的情況下，其穩(wěn)定性也得到了良好保障。
3.良好的兼容性
FTL技術與現(xiàn)有的操作系統(tǒng)兼容性非常良好，無需專門針對某一種操作系統(tǒng)的設計，可以廣泛使用于各種系統(tǒng)中。
四、
總體而言，隨著信息的不斷更新，感知持續(xù)變化下的技術發(fā)展需求，Linux FTL通用設備層將會在存儲介質的發(fā)展中發(fā)揮更大的作用。Linux FTL通用設備層技術已經(jīng)被大量應用于移動設備、車載娛樂系統(tǒng)、工業(yè)控制等領域，具有良好的可擴展性，穩(wěn)定性和兼容性。未來，Linux FTL通用設備層還將不斷發(fā)展，為存儲技術的創(chuàng)新打下堅實的基礎。
相關問題拓展閱讀：
- LINUX 終端設備驅動？
- 求有關linux的英文資料！！謝謝
- LINUX系統(tǒng)的特點是什么
LINUX 終端設備驅動？
在Linux系統(tǒng)中，終端是一種字符型設備，它有多種類型，通常使用tty (Teletype）來簡稱各種類型的終端設備。對于嵌入式系統(tǒng)而言，最普遍采用的是UART (Universal Asynchronous Receiver/Tranitter)串行端口，日常生活中簡稱串口。
Linux內核中tty的層次結構它包含tty核心tty_10.c、tty或路規(guī)在n_tty.C(頭現(xiàn)N_11Y線路規(guī)程）和tty驅動實例xxx_tty.c，激慧tty線路規(guī)程的工作是以特殊的方式格式化從一個用戶或者硬件收到的數(shù)據(jù)，這種格式化常常采用一個協(xié)議轉換的形式tty _io.c本身是一個標準的字符設備驅動，它對上有字符改備的職貢，買現(xiàn)tle_operatIonS雙貝圖效。但是tty核心層對下又定義了tty_driver的架構，這樣tty設備驅動的主體工作就變成了琪允tty_driVeT依構體中的成員，實現(xiàn)其中的tty_operations的成員函數(shù)，而不再是去實現(xiàn)file_operations這一級的工作。tty設枯衡備發(fā)送數(shù)據(jù)的流程為:tty核心從一個用戶獲取將要發(fā)送給一個tty設備的數(shù)據(jù)，tty核心將數(shù)據(jù)傳遞給tty線路規(guī)程驅動，接著數(shù)據(jù)被傳遞到tty驅動，tty驅動將數(shù)據(jù)轉換為可以發(fā)送給硬件的格式。接收數(shù)據(jù)的流程為:從tty硬件接收到的數(shù)據(jù)向上交給tty驅動，接著進入tty線路規(guī)程驅動，再進入tty核心，在這里它被一個用戶獲取。盡管一個特定的底層UART設備驅動完全可以遵循上述tty_driver的方法來設計，即定義tty_driver并實現(xiàn)tty_operations中的成員函數(shù)，但是鑒于串口之間的共性，Linux考慮在文件drivers’ttyliserial’serial_core.c中實現(xiàn)了UART設備的通用tty驅動層（我們可以稱其為串口核心層)。這樣，UART驅動的明敗答主要任務就進一步演變成了實現(xiàn)serial-core.c中定義的一組uart_xxx接口而不是tty_xxx接口。因此，按照面向對象的思想，可以認為tty_driver是字符設備的泛化、serial-core是tty_driver的泛化，而具體的串口驅動又是serial-core的泛化。
求有關linux的英文資料??！謝謝
wiki網(wǎng)站，看linux詞條。。。
Anatomy of Linux flash file systems
Options and architectures
Summary: You’ve probably heard of Journaling Flash File System (JFFS) and Yet
Another Flash File System (YAFFS), but do you know what it means to have a file
system that assumes an underlying flash device? This article introduces you to
flash file systems for Linux?, explores how they care for their underlying
consumable devices (flash parts) through wear leveling, and identifies the
various flash file systems available along with their fundamental designs.
Solid-state drives are all the rage these days, but embedded systems have
used solid-state devices for storage for quite some time. You’ll find flash
file systems used in personal digital assistants (PDAs), cell phones, MP3
players, digital cameras, USB flash drives (UFDs), and even laptop computers.
In many cases, the file systems for commercial devices can be custom and
proprietary, but they face the same challenges discussed below.
Flash-based file systems come in a variety of forms. This article explores
a couple of the read-only file systems and also reviews the various read/write
file systems available today and how they work. But first, let’s explore the
flash devices and the challenges that they introduce.
Flash memory technologies
Flash memory, which can come in several different technologies, is non-volatile
memory, which means that its contents persist after its source of power is
removed. For a great history of flash memory devices, see Resources.
Two of the most common types of flash devices are defined by their
respective technologies: NOR and NAND. NOR-based flash is the older technology
that supported high read performance at the expense of aller capacities. NAND
flash offers higher capacities with significantly faster write and erase
performance. NAND also requires a much more complicated input/output (I/O)
interface.
Flash parts are commonly divided into partitions, which allows
multiple operations to occur simultaneously (erasing one partition while
reading from another). Partitions are further divided into blocks
(commonly 64KB or 128KB in size). Firmware that uses the partitions can further
apply unique segmenting to the blocks—for example, 512-byte segments within a
block, not including metadata.
Flash devices exhibit a common constraint that requires device management
when compared to other storage devices such as RAM disks. The only Write
operation permitted on a flash memory device is to change a bit from a one to a
zero. If the reverse operation is needed, then the block must be erased (to
reset all bits to the one state). This means that other valid data within the
block must be moved for it to persist. NOR flash memory can typically be
programmed a byte at a time, whereas NAND flash memory must be programmed in
multi-byte bursts (typically, 512 bytes).
The process of erasing a block differs between the two memory types. Each
requires a special Erase operation that covers an entire block of the flash
memory. NOR technology requires a precursor step to clear all values to zero
before the Erase operation can begin. An Erase is a special operation
with the flash device and can be time-consuming. Erasing is an electrical
operation that drains the electrons from each cell in an entire block.
NOR flash devices typically require seconds for the Erase operation,
whereas a NAND device can erase in milliseconds. A key characteristic of flash
devices is the number of Erase operations that can be performed. In a NOR
device, each block in the flash memory can be erased up to 100,000 times. NAND
flash memories can be erased up to one million times.
Flash memory challenges
In addition to and as a result of the constraints explored in the previous
section, managing flash devices presents several challenges. The three most
important are garbage collection, managing bad blocks, and wear leveling.
Garbage collection
Garbage collection is the process of reclaiming invalid blocks (those that
contain some amount of invalid data). Reclamation involves moving the valid
data to a new block, and then erasing the invalid block to make it available.
This process is commonly done in the background or as needed, if the file
system is low on available space.
Managing bad blocks
Over time, flash devices can develop bad blocks through use and can even
ship from the manufacturer with blocks that are bad and cannot be used. You can
detect the presence of back blocks from a failed flash operation (such as an
Erase) or an invalid Write operation (discovered through an invalid Error
Correction Code, or ECC).
After bad blocks have been identified, they are marked within the flash
itself in a bad block table. How this is done is device-dependent but can be
implemented with a separate set of reserved blocks managed separately from
normal data blocks. The process of handling bad blocks—whether they ship with
the device or appear over time—is called bad block management. In some
cases, this functionality is implemented in hardware by an internal
microcontroller and is therefore transparent to the upper-level file system.
Wear leveling
Recall that flash devices are consumable parts: You can perform a finite
number of Erase cycles on each block before the block becomes bad (and must
therefore be tagged by bad block management). To maximize the life of the
flash, wear-leveling algorithms are provided. Wear leveling comes in two
varieties: dynamic wear leveling and static wear leveling.
Dynamic wear leveling addresses the problem of a limited number of Erase
cycles for a given block. Rather than randomly using blocks as they are
available, dynamic wear-leveling algorithms attempt to evenly distribute the
use of blocks so that each gets uniform use. Static wear-leveling algorithms
address an even more interesting problem. In addition to a maximum number of
Erase cycles, certain flash devices suffer from a maximum number of Read cycles
between Erase cycles. This means that if data sits for too long in a block and
is read too many times, the data can dissipate and result in data loss. Static
wear-leveling algorithms address this by periodically moving stale data to new
blocks.
System architecture
So far, I’ve explored flash devices and their fundamental challenges. Now,
look at how these pieces come together as part of a layered architecture (see
Figure 1). At the top is the virtual file system (VFS), which presents a common
interface to higher-level applications. The VFS is followed by the flash file
system, which will be covered in the next section. Next is the Flash
Translation Layer (FTL), which provides for overall management of the flash
device, including allocation of blocks from the underlying flash device as well
as address translation, dynamic wear leveling, and garbage collection. In some
flash devices, a portion of the FTL can be implemented in hardware.
The Linux kernel uses the Memory Technology Device (MTD) interface, which
is a generic interface for flash devices. The MTD can automatically detect the
width of the flash device bus and the number of devices necessary for
implementing the bus width.
Flash file systems
Several flash file systems are available for Linux. The next sectionsexplain the design and advantages of each.
Journaling Flash File System
One of the earliest flash file systems for Linux is called the Journaling
Flash File System. JFFS is a log-structured file system that was designed
for NOR flash devices. It was unique and addressed a variety of problems with
flash devices, but it created another.
JFFS viewed the flash device as a circular log of blocks. Data written to
the flash is written to the tail, and blocks at the head are reclaimed. The
space between the tail and head is free space; when this space becomes low, the
garbage collector is executed. The garbage collector moves valid blocks to the
tail of the log, skips invalid or obsolete blocks, and erases them (see Figure
2). The result is a file system that is automatically wear leveled both
statically and dynamically. The fundamental problem with this architecture is
that the flash device is erased too often (instead of an optimal erase
strategy), which wears the device out too quickly.
When a JFFS is mounted, the structural details are read into memory, whichcan be slow at mount-time and consume more memory than desired.
Journaling Flash File System 2
Although JFFS was very useful in its time, its wear-leveling algorithm
tended to shorten the life of NOR flash devices. The result was a redesign of
the underlying algorithm to remove the circular log. The JFFS2 algorithm was
designed for NAND flash devices and also includes improved performance with
compression.
In JFFS2, each block in the flash is treated independently. JFFS2 maintains
block lists to sufficiently wear-level the device. The clean list represents
blocks on the device that are full of valid nodes. The dirty list contains
blocks with at least one obsoleted node. Finally, the free list represents the
blocks that have been erased and are available for use.
The garbage collection algorithm can then intelligently decide what to
reclaim in a reasonable way. Currently, the algorithm probabilistically selects
from the clean or dirty list. The dirty list is selected 99 percent of the time
to reclaim blocks (moving the valid contents to another block), and the clean
list is selected 1 percent of the time (simply moving the contents to a new
block). In both cases, the selected block is erased and placed on the free list
(see Figure 3). This allows the garbage collector to re-use blocks that are
obsoleted (or partially so) but still move data around the flash to support
static wear leveling.
Yet Another Flash File System
YAFFS is another flash file system developed for NAND flash. The initial
version (YAFFS) supported flash devices with 512-byte pages, but the newer
version (YAFFS2) supports newer devices with larger page sizes and greater
Write constraints.
In most flash file systems, obsolete blocks are marked as such, but YAFFS2
additionally marks blocks with monotonically increasing sequence numbers. When
the file system is scanned at mount time, the valid inodes can be quickly
identified. YAFFS also maintains trees in RAM to represent the block structure
of the flash device, including fast mounting through checkpointing —the
process of saving the RAM tree structure to the flash device on a normal
unmount so that it can be quickly read and restored to RAM at mount time (see
Figure 4). Mount-time performance is a great advantage of YAFFS2 over other
flash file systems.
Read-only compressed file systems
In some embedded systems, there’s no need to provide a mutable file system:
An immutable one will suffice. Linux supports a variety of read-only file
systems, two of the most useful are cramfs and SquashFS.
Cramfs
The cramfs file system is a compressed read-only Linux file system that can
exist within flash devices. The primary characteristics of cramfs are that it
is both simple and space-efficient. This file system is used in all-footprint
embedded designs.
While cramfs metadata is not compressed, cramfs uses zlib compression on a
per-page basis to allow random page access (pages are decompressed upon
access).
You can play with cramfs using the mkcramfs utility and the loopbackdevice.
SquashFS
SquashFS is another compressed read-only Linux file system that is useful
within flash devices. You’ll also find SquashFS in numerous Live CD Linux
distributions. In addition to supporting zlib for compression, SquashFS uses
Lembel-Ziv-Markov chain Algorithm (LZMA) for improved compression and speed.
Like cramfs, you can use SquashFS on a standard Linux system withmksquashfs and the loopback device.
Going further
Like most of open source, software continues to evolve, and new flash file
systems are under development. An interesting alternative still in development
is LogFS, which includes some very novel ideas. For example, LogFS maintains a
tree structure on the flash device itself so that the mount times are similar
to traditional file systems, such as ext2. It also uses a wandering tree for
garbage collection (a form of B+tree). What makes LogFS particularly
interesting, however, is that it is very scalable and can support large flash
parts.
With the growing popularity of flash file systems, you’ll see a
considerable amount of research being applied toward them. LogFS is one
example, but other options, such as UbiFS, are also growing. Flash file systems
are interesting architecturally and will continue to be a source of innovationin the future.
google之，
最簡單的是 google學術里面輸入 linux 搜索你要的文獻
郵箱留下，傳給你
LINUX系統(tǒng)的特點是什么
Linux（i/?l?n?ks/LIN-?ks）是一種自由和開放源碼的類UNIX操作系統(tǒng)。該操作系統(tǒng)的內核由林納斯·托瓦茲在1991年10月5日首次渣段高發(fā)布，在加上用戶空間的應用程序之后，成為Linux操作系統(tǒng)。
Linux也是自由軟件和開放源代碼軟件發(fā)展中最著名的例子。只要遵循GNU通用公共許可證（GPL），任何個人和機構都可以自由地使燃慧用Linux的所有底層源代碼，也可以自由地修改和再發(fā)布。大多數(shù)Linux系統(tǒng)還包括像提供GUI的XWindow之類的程序。
LINUX系統(tǒng)的特點
1、Linux是一款免費的操作系統(tǒng)，用戶可以通過網(wǎng)絡或其他途徑免費獲得，并可以任意修改其源代碼。這是其他的操作系統(tǒng)所做不到的。
2、在Linux下通過相應的模擬器運行常見的DOS、Windows的程序。這為用戶從Windows轉到Linux奠定了基礎。
3、Linux可以運行在多種硬件平臺上，如具有x86、680×0、SPARC、Alpha等處如尺理器的平臺。此外Linux還是一種嵌入式操作系統(tǒng)，可以運行在掌上電腦、機頂盒或游戲機上。
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