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Flashcache
Flashcache is a disk cache component for the Linux kernel, initially developed by Facebook since April 2010, and released as open source in 2011. Since January 2013, there is a fork of Flashcache, named EnhanceIO and developed by sTec, Inc. Since 2015 that fork became unmaintained and it was forked again and maintained by individuals. Flashcache works by using flash memory, a USB flash drive, SD card, CompactFlash or any kind of portable flash mass storage system as a write-back persistent cache. An internal SSD can also be used for increasing performance. Overview Using flash memory ( NAND memory devices) for caching allows Linux kernel to service random disk IO with better performance than without the cache. This caching applies to all disk content, not just the page file or system binaries. Flash memory based devices are usually a magnitude faster than spinning HDDs for random IO, but with less advantage or even slower in sequential read/writes. By default, flashcache ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EnhanceIO
EnhanceIO is a disk cache module for the Linux kernel. Its goal is to use fast but relatively small SSD drives to improve the performance of large but slow hard drives. Overview EnhanceIO makes it possible to add an SSD or other fast disk device as a cache to another block device, such as a hard drive, in order to improve the performance of the disk. It was initially based on Facebook's similar Flashcache module. Unlike Flashcache and other caching solutions, it doesn't use the Linux device mapper. This means it does not create a new block device and caching can be added to existing disks, without reformatting or even unmounting them. This makes it easy to add cache to existing systems. History EnhanceIO was first announced as a commercial product in 2011 by sTec Inc, a company specializing in SSD products. Late 2012 sTec published code for the Linux module on GitHub. Even though it was then soon submitted to the Linux kernel mailing list, it was never merged into the main kernel. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dm-cache
dm-cache is a component (more specifically, a target) of the Linux kernel's device mapper, which is a framework for mapping block devices onto higher-level virtual block devices. It allows one or more fast storage devices, such as flash-based solid-state drives (SSDs), to act as a cache for one or more slower storage devices such as hard disk drives (HDDs); this effectively creates hybrid volumes and provides secondary storage performance improvements. The design of dm-cache requires three physical storage devices for the creation of a single hybrid volume; dm-cache uses those storage devices to separately store actual data, cache data, and required metadata. Configurable operating modes and cache policies, with the latter in the form of separate modules, determine the way data caching is actually performed. dm-cache is licensed under the terms of GNU General Public License (GPL), with Joe Thornber, Heinz Mauelshagen and Mike Snitzer as its primary developers. Overview d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bcache
bcache (abbreviated from ''block cache'') is a cache in the Linux kernel's block layer, which is used for accessing secondary storage devices. It allows one or more fast storage devices, such as flash-based solid-state drives (SSDs), to act as a cache for one or more slower storage devices, such as hard disk drives (HDDs); this effectively creates hybrid volumes and provides performance improvements. Designed around the nature and performance characteristics of SSDs, bcache also minimizes write amplification by avoiding random writes and turning them into sequential writes instead. This merging of I/O operations is performed for both the cache and the primary storage, helping in extending the lifetime of flash-based devices used as caches, and in improving the performance of write-sensitive primary storages, such as RAID 5 sets. bcache is licensed under the GNU General Public License (GPL), and Kent Overstreet is its primary developer. Overstreet considers bcache as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solid-state Drive
A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is also sometimes called a semiconductor storage device, a solid-state device or a solid-state disk, even though SSDs lack the physical spinning disks and movable read–write heads used in hard disk drives (HDDs) and floppy disks. SSD also has rich internal parallelism for data processing. In comparison to hard disk drives and similar electromechanical media which use moving parts, SSDs are typically more resistant to physical shock, run silently, and have higher input/output rates and lower latency. SSDs store data in semiconductor cells. cells can contain between 1 and 4 bits of data. SSD storage devices vary in their properties according to the number of bits stored in each cell, with single-bit cells ("Single Level Cells" or " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NetApp
NetApp, Inc. is an American hybrid cloud data services and data management company headquartered in San Jose, California. It has ranked in the Fortune 500 from 2012–2021. Founded in 1992 with an IPO in 1995, NetApp offers cloud data services for management of applications and data both online and physically. History NetApp was founded in 1992 by David Hitz, James Lau, and Michael Malcolm as Network Appliance, Inc. At the time, its major competitor was Auspex Systems. In 1994, NetApp received venture capital funding from Sequoia Capital. It had its initial public offering in 1995. NetApp thrived in the internet bubble years of the mid 1990s to 2001, during which the company grew to $1 billion in annual revenue. After the bubble burst, NetApp's revenues quickly declined to $800 million in its fiscal year 2002. Since then, the company's revenue has steadily climbed. In 2006, NetApp sold the NetCache product line to Blue Coat Systems. In 2008, Network Appliance o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of Microsoft Windows desktop operating systems. Development was completed on November 8, 2006, and over the following three months, it was released in stages to computer hardware and software manufacturers, business customers and retail channels. On January 30, 2007, it was released internationally and was made available for purchase and download from the Windows Marketplace; it is the first release of Windows to be made available through a digital distribution platform. New features of Windows Vista include an updated graphical user interface and visual style dubbed Aero, a new search component called Windows Search, redesigned networking, audio, print and display sub-systems, and new multimedia tools such as Windows DVD Maker. Vist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LKML
The Linux kernel mailing list (LKML) is the main electronic mailing list for Linux kernel development, where the majority of the announcements, discussions, debates, and flame wars over the kernel take place. Many other mailing lists exist to discuss the different subsystems and ports of the Linux kernel, but LKML is the principal communication channel among Linux kernel developers. It is a very high-volume list, usually receiving about 1,000 messages each day, most of which are kernel code patches. Linux utilizes a workflow governed by LKML, which is the " bazaar" where kernel development takes place. In his book ''Linux Kernel Development'', Robert Love notes: The LKML functions as the central place where Linux developers around the world share patches, argue about implementation details, and discuss other issues. The official releases of the Linux kernel are indicated by an email to LKML. New features are discussed and most code is posted to the list before any action is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache Acceleration Software
The Intel Cache Acceleration Software (CAS) is a computer data storage product for solid-state drive (SSD) caching. Description CAS manages using the SSD storage as a cache layer for slower storage data (e.g. spinning hard drives). A cached copy of recently used data from slower storage is kept in faster SSD storage to improve I/O performance. CAS entered Intel's product line as the result of Intel's August 2012 acquisition of a Canadian start-up company Nevex Virtual Technologies; Intel re-branded Nevex CacheWorks product to CAS with the release of version 2.0 in December 2012. Versions of Intel CAS are available for Windows Enterprise, Windows Workstation, and Linux. CAS for Windows is an application-aware file-based cache, which can be tuned by system administrators. Additionally, it integrates with the operating system's buffer cache, creating a multi-tier cache architecture. CAS is also aware of some virtualization technologies like vMotion, maintaining a hot SSD cache during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trim (computing)
A trim command (known as TRIM in the ATA command set, and UNMAP in the SCSI command set) allows an operating system to inform a solid-state drive (SSD) which blocks of data are no longer considered to be 'in use' and therefore can be erased internally. Trim was introduced soon after SSDs were introduced. Because low-level operation of SSDs differs significantly from hard drives, the typical way in which operating systems handle operations like deletes and formats resulted in unanticipated progressive performance degradation of write operations on SSDs. Trimming enables the SSD to more efficiently handle garbage collection, which would otherwise slow future write operations to the involved blocks.Shimpi, Anand Lal. (18 March 2009). p. 10. TRIM is an ATA command (Advanced Technology Attachment Command) that allows an OS to inform SSD about the blocks of data no longer in use. The SSD then deletes such blocks of data to make a way for newer blocks of data. TRIM is basically used ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write-back
In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A ''cache hit'' occurs when the requested data can be found in a cache, while a ''cache miss'' occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs. To be cost-effective and to enable efficient use of data, caches must be relatively small. Nevertheless, caches have proven themselves in many areas of computing, because typical computer applications access data with a high degree of locality of reference. Such access patterns exhibit temporal locality, where data is requested that has been recently requested already, and spatial locality, where da ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear Probing
Linear probing is a scheme in computer programming for resolving collisions in hash tables, data structures for maintaining a collection of key–value pairs and looking up the value associated with a given key. It was invented in 1954 by Gene Amdahl, Elaine M. McGraw, and Arthur Samuel and first analyzed in 1963 by Donald Knuth. Along with quadratic probing and double hashing, linear probing is a form of open addressing. In these schemes, each cell of a hash table stores a single key–value pair. When the hash function causes a collision by mapping a new key to a cell of the hash table that is already occupied by another key, linear probing searches the table for the closest following free location and inserts the new key there. Lookups are performed in the same way, by searching the table sequentially starting at the position given by the hash function, until finding a cell with a matching key or an empty cell. As write, "Hash tables are the most commonly used nontrivial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hash Table
In computing, a hash table, also known as hash map, is a data structure that implements an associative array or dictionary. It is an abstract data type that maps keys to values. A hash table uses a hash function to compute an ''index'', also called a ''hash code'', into an array of ''buckets'' or ''slots'', from which the desired value can be found. During lookup, the key is hashed and the resulting hash indicates where the corresponding value is stored. Ideally, the hash function will assign each key to a unique bucket, but most hash table designs employ an imperfect hash function, which might cause hash '' collisions'' where the hash function generates the same index for more than one key. Such collisions are typically accommodated in some way. In a well-dimensioned hash table, the average time complexity for each lookup is independent of the number of elements stored in the table. Many hash table designs also allow arbitrary insertions and deletions of key–value pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
