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57-717: It is sometimes referred to as a virtual RAM drive or software RAM drive to distinguish it from a hardware RAM drive that uses separate hardware containing RAM, which is a type of battery-backed solid-state drive . Historically primary storage based mass storage devices were conceived to bridge the performance gap between internal memory and secondary storage devices. In the advent of solid-state devices this advantage lost most of its appeal. However, solid-state devices do suffer from wear from frequent writing. Primary memory writes do not so or in far lesser effect. So RAM devices do offer an advantage to store frequently changing data, like temporary or cached information. The performance of

114-475: A Samsung 970 EVO NVMe M.2 SSD (2018) with 1 TB of capacity has an endurance rating of 600 TBW. Recovering data from SSDs presents challenges due to the non-linear and complex nature of data storage in solid-state drives. The internal operations of SSDs vary by manufacturer, with commands (e.g. TRIM and the ATA Secure Erase) and programs like (e.g. hdparm ) being able to erase and modify

171-428: A cache (configurable as write-through or write-back ) for a conventional, magnetic hard disk drive. A similar technology is available on HighPoint 's RocketHybrid PCIe card. Solid-state hybrid drives (SSHDs) are based on the same principle, but integrate some amount of flash memory on board of a conventional drive instead of using a separate SSD. The flash layer in these drives can be accessed independently from

228-409: A live SD operating system are easily write-locked . Combined with a cloud computing environment or other writable medium, an OS booted from a write-locked SD card is reliable, persistent and impervious to permanent corruption. In 2011, Intel introduced a caching mechanism for their Z68 chipset (and mobile derivatives) called Smart Response Technology , which allows a SATA SSD to be used as

285-540: A RAM drive is generally orders of magnitude faster than other forms of digital storage, such as SSD , tape , optical , hard disk , and floppy drives. This performance gain is due to multiple factors, including access time, maximum throughput , and file system characteristics. File access time is greatly reduced since a RAM drive is solid state (no moving parts). A physical hard drive, optical (e.g, CD-ROM , DVD , and Blu-ray ) or other media (e.g. magnetic bubble , acoustic storage , magnetic tape ) must move

342-599: A RAM drive named /RAM . IBM added a RAM drive named VDISK.SYS to PC DOS (version 3.0) in August 1984, which was the first DOS component to use extended memory . VDISK.SYS was not available in Microsoft 's MS-DOS as it, unlike most components of early versions of PC DOS, was written by IBM. Microsoft included the similar program RAMDRIVE.SYS in MS-DOS 3.2 (released in 1986), which could also use expanded memory . It

399-411: A constant power supply to retain data. DRAM-based SSDs are typically used in specialized applications where performance is prioritized over cost or non-volatility. Many SSDs, such as NVDIMM devices, are equipped with backup power sources such as internal batteries or external AC/DC adapters. These power sources ensure data is transferred to a backup system (usually NAND flash or another storage medium) in

456-471: A constant power supply. NAND flash-based SSDs store data in semiconductor cells, with the specific architecture influencing performance, endurance, and cost. There are various types of NAND flash memory, categorized by the number of bits stored in each cell: Over time, SSD controllers have improved the efficiency of NAND flash, incorporating techniques such as interleaved memory , advanced error correction, and wear leveling to optimize performance and extend

513-807: A controller, which manages the data flow between the NAND memory and the host computer. The controller is an embedded processor that runs firmware to optimize performance, managing data, and ensuring data integrity. Some of the primary functions performed by the controller are: The overall performance of an SSD can scale with the number of parallel NAND chips and the efficiency of the controller. For example, controllers that enable parallel processing of NAND flash chips can improve bandwidth and reduce latency. Micron and Intel pioneered faster SSDs by implementing techniques such as data striping and interleaving to enhance read/write speeds. More recently, SandForce introduced controllers that incorporate data compression to reduce

570-525: A disk drive was much faster than the disk drives. especially before hard drives were readily available on such machines. The Silicon Disk was launched in 1980, initially for the CP/M operating system and later for MS-DOS . The 128kB Atari 130XE (with DOS 2.5) and Commodore 128 natively support RAM drives, as does ProDOS for the Apple II . On systems with 128kB or more of RAM, ProDOS automatically creates

627-413: A few specialized "ultra-lightweight" Linux distributions which are designed to boot from removable media and stored in a ramdisk for the entire session. There have been RAM drives which use DRAM memory that is exclusively dedicated to function as an extremely low latency storage device. This memory is isolated from the processor and not directly accessible in the same manner as normal system memory. Some of

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684-743: A limited lifetime number of writes, and also slow down as they reach their full storage capacity. SSDs also have internal parallelism that allows them to manage multiple operations simultaneously, which enhances their performance. Unlike HDDs and similar electromechanical magnetic storage , SSDs do not have moving mechanical parts, which provides advantages such as resistance to physical shock, quieter operation, and faster access times. Their lower latency results in higher input/output rates (IOPS) than HDDs. Some SSDs are combined with traditional hard drives in hybrid configurations, such as Intel's Hystor and Apple's Fusion Drive . These drives use both flash memory and spinning magnetic disks in order to improve

741-864: A lower cost than pure SSDs. An SSD stores data in semiconductor cells, with its properties varying according to the number of bits stored in each cell (between 1 and 4). Single-level cells (SLC) store one bit of data per cell and provide higher performance and endurance. In contrast, multi-level cells (MLC), triple-level cells (TLC), and quad-level cells (QLC) store more data per cell but have lower performance and endurance. SSDs using 3D XPoint technology, such as Intel’s Optane, store data by changing electrical resistance instead of storing electrical charges in cells, which can provide faster speeds and longer data persistence compared to conventional flash memory. SSDs based on NAND flash slowly leak charge when not powered, while heavily-used consumer drives may start losing data typically after one to two year in storage. SSDs have

798-513: A pair of Serial ATA ports, allowing it to function as a single drive or masquerade as a pair of drives that can easily be split into an even faster RAID 0 array." In 2009, Acard Technology produced the ACARD ANS-9010BA 5.25 Dynamic SSD SATA-II RAM Disk, max 64GB. It uses a single SATA-II port. Both variants are equipped with one or more CompactFlash card interface located in the front panel, allowing non-volatile data being stored on

855-470: A partition on a physical hard drive rather than accessing the data bus normally used for secondary storage. Though RAM drives can often be supported directly in the operating system via special mechanisms in the OS kernel , it is generally simpler to access a RAM drive through a virtual device driver. This makes the non-disk nature of RAM drives invisible to both the OS and applications. Usually no battery backup

912-474: A reliable backup. In 2009, DDRdrive, LLC produced the DDRDrive X1, which claims to be the fastest solid state drive in the world. The drive is a primary 4GB DDR dedicated RAM drive for regular use, which can back up to and recall from a 4GB SLC NAND drive. The intended market is for keeping and recording log files . If there is a power loss the data can be saved to an internal 4GB ssd in 60 seconds, via

969-616: A selling feature. Later, the ASDG RRD was made available as shareware carrying a suggested donation of 10 dollars. The shareware version appeared on Fred Fish Disks 58 and 241. AmigaOS itself would gain a Recoverable Ram Disk (called "RAD") in version 1.3. Many Unix and Unix-like systems provide some form of RAM drive functionality, such as /dev/ram on Linux , or md(4) on FreeBSD . RAM drives are particularly useful in high-performance, low-resource applications for which Unix-like operating systems are sometimes configured. There are also

1026-936: A small amount of volatile DRAM as a cache, similar to the buffers in hard disk drives. This cache can temporarily hold data while it is being written to the flash memory, and it also stores metadata such as the mapping of logical blocks to physical locations on the SSD. Some SSD controllers, like those from SandForce, achieve high performance without using an external DRAM cache. These designs rely on other mechanisms, such as on-chip SRAM, to manage data and minimize power consumption. Additionally, some SSDs use an SLC cache mechanism to temporarily store data in single-level cell (SLC) mode, even on multi-level cell (MLC) or triple-level cell (TLC) SSDs. This improves write performance by allowing data to be written to faster SLC storage before being moved to slower, higher-capacity MLC or TLC storage. On NVMe SSDs, Host Memory Buffer (HMB) technology allows

1083-601: A sudden power loss. Some consumer SSDs have built-in capacitors to save critical data such as the Flash Translation Layer (FTL) mapping table. Examples include the Crucial M500 and Intel 320 series. Enterprise-class SSDs, such as the Intel DC S3700 series, often come with more robust power-loss protection mechanisms like supercapacitors or batteries. The host interface of an SSD refers to

1140-735: A system in the same way as HDDs, SSDs are used in a variety of devices, including personal computers , enterprise servers , and mobile devices . However, SSDs are generally more expensive on a per-gigabyte basis and have a finite number of write cycles, which can lead to data loss over time. Despite these limitations, SSDs are increasingly replacing HDDs, especially in performance-critical applications and as primary storage in many consumer devices. SSDs come in various form factors and interface types, including SATA , PCIe , and NVMe , each offering different levels of performance. Hybrid storage solutions, such as solid-state hybrid drives (SSHDs), combine SSD and HDD technologies to offer improved performance at

1197-557: Is a free ( GPL 'ed) read-only Linux file system designed for simplicity and space-efficiency. It is mainly used in embedded and small-footprint systems. Unlike a compressed image of a conventional file system, a cramfs image can be used as it is, i.e. without first decompressing it. For this reason, some Linux distributions use cramfs for initrd images ( Debian 3.1 in particular) and installation images ( SUSE Linux in particular), where there are constraints on memory and image size. In 2013, Linux maintainers indicated that cramfs

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1254-496: Is infrequently changed (cold data) from heavily used blocks, so that data that changes more frequently (hot data) can be written to those blocks. This helps distribute wear more evenly across the entire SSD. However, this process introduces additional writes, known as write amplification, which must be managed to balance performance and durability. Most SSDs use non-volatile NAND flash memory for data storage, primarily due to its cost-effectiveness and ability to retain data without

1311-548: Is needed due to the temporary nature of the information stored in the RAM drive, but an uninterruptible power supply can keep the system running during a short power outage. Some RAM drives use a compressed file system such as cramfs to allow compressed data to be accessed on the fly, without decompressing it first. This is convenient because RAM drives are often small due to the higher price per byte than conventional hard drive storage. The first software RAM drive for microcomputers

1368-446: Is the speed of the actual mechanics of the drive motors, heads, or eyes. Third, the file system in use, such as NTFS , HFS , UFS , ext2, etc., uses extra accesses, reads and writes to the drive, which although small, can add up quickly, especially in the event of many small files vs. few larger files (temporary internet folders, web caches, etc.). Because the storage is in RAM, it is volatile memory , which means it will be lost in

1425-692: The GC-RAMDISK , max 8GB, which was the second generation creation for the i-RAM. It has a maximum of 8 GB capacity, twice that of the i-RAM. It used the SATA-II port, again twice that of the i-RAM. One of its best selling points is that it can be used as a boot device. In 2007, ACard Technology produced the ANS-9010 Serial ATA RAM disk, max 64 GB. Quote from the tech report: The ANS-9010 "which has eight DDR2 DIMM slots and support for up to 8 GB of memory per slot. The ANS-9010 also features

1482-467: The i-RAM , max 4 GB, which functioned essentially identically to the Rocket Drive, except upgraded to use the newer DDR memory technology, though also limited to a maximum of 4 GB capacity. For both of these devices, the dynamic RAM requires continuous power to retain data; when power is lost, the data fades away. For the Rocket Drive, there was a connector for an external power supply separate from

1539-466: The magnetic storage by the host using ATA-8 commands, allowing the operating system to manage it. For example, Microsoft's ReadyDrive technology explicitly stores portions of the hibernation file in the cache of these drives when the system hibernates, making the subsequent resume faster. Dual-drive hybrid systems are combining the usage of separate SSD and HDD devices installed in the same computer, with overall performance optimization managed by

1596-569: The RAM drive to be copied on the CompactFlash card in case of power failure and low backup battery. Two pushbuttons located on the front panel allows the user to manually backup / restore data on the RAM drive. The CompactFlash card itself is not accessible to the user by normal means as the CF card is solely intended for RAM backup and restoration. The CF card's capacity has to meet / exceed the RAM module's total capacity in order to effectively work as

1653-508: The SSD to use a portion of the system’s DRAM instead of relying on a built-in DRAM cache, reducing costs while maintaining a high level of performance. In certain high-end consumer and enterprise SSDs, larger amounts of DRAM are included to cache both file table mappings and written data, reducing write amplification and enhances overall performance. Higher-performing SSDs may include a capacitor or battery, which helps preserve data integrity in

1710-450: The amount of data written to the flash memory, potentially increasing both performance and endurance. Wear leveling is a technique used in SSDs to ensure that write and erase operations are distributed evenly across all blocks of the flash memory. Without this, specific blocks could wear out prematurely due to repeated use, reducing the overall lifespan of the SSD. The process moves data that

1767-418: The bits of a deleted file. The JEDEC Solid State Technology Association (JEDEC) has established standards for SSD reliability metrics, which include: In a distributed computing environment, SSDs can be used as a distributed cache layer that temporarily absorbs the large volume of user requests to slower HDD-based backend storage systems. This layer provides much higher bandwidth and lower latency than

RAM drive - Misplaced Pages Continue

1824-426: The complete loss of the drive. Most of the advantages of solid-state drives over traditional hard drives are due to their ability to access data completely electronically instead of electromechanically, resulting in superior transfer speeds and mechanical ruggedness. On the other hand, hard disk drives offer significantly higher capacity for their price. In traditional HDDs, a rewritten file will generally occupy

1881-691: The computer like hard drives. In contrast, memory cards (such as Secure Digital (SD), CompactFlash (CF), and many others) were originally designed for digital cameras and later found their way into cell phones, gaming devices, GPS units, etc. Most memory cards are physically smaller than SSDs, and designed to be inserted and removed repeatedly. SSDs have different failure modes from traditional magnetic hard drives. Because solid-state drives contain no moving parts, they are generally not subject to mechanical failures. However, other types of failures can occur. For example, incomplete or failed writes due to sudden power loss may be more problematic than with HDDs, and

1938-593: The computer user, or by the computer's operating system software. Examples of this type of system are bcache and dm-cache on Linux , and Apple's Fusion Drive . The primary components of an SSD are the controller and the memory used to store data. Traditionally, early SSDs used volatile DRAM for storage, but since 2009, most SSDs utilize non-volatile NAND flash memory, which retains data even when powered off. Flash memory SSDs store data in metal–oxide–semiconductor (MOS) integrated circuit chips, using non-volatile floating-gate memory cells. Every SSD includes

1995-629: The computer, and the option for an external battery to retain data during a power failure. The i-RAM included a small battery directly on the expansion board, for 10-16 hours of protection. Both devices used the SATA 1.0 interface to transfer data from the dedicated RAM drive to the system. The SATA interface was a slow bottleneck that limited the maximum performance of both RAM drives, but these drives still provided exceptionally low data access latency and high sustained transfer speeds, compared to mechanical hard drives. In 2006, Gigabyte Technology produced

2052-439: The data stored on the RAM drive is created from data permanently stored elsewhere, for faster access , and is re-created on the RAM drive when the system reboots. Apart from the risk of data loss, the major limitation of RAM drives is capacity, which is constrained by the amount of installed RAM. Multi-terabyte SSD storage has become common, but RAM is still measured in gigabytes. RAM drives use normal system memory as if it were

2109-509: The electrical resistance of materials in its cells, offering much faster access times than NAND flash. 3D XPoint-based SSDs, such as Intel’s Optane drives, provide lower latency and higher endurance than NAND-based drives, although they are more expensive per gigabyte. Drives known as hybrid drives or solid-state hybrid drives (SSHDs) use a hybrid of spinning disks and flash memory. Some SSDs use magnetoresistive random-access memory (MRAM) for storing data. Many flash-based SSDs include

2166-535: The event of an unexpected power loss. The capacitor or battery provides enough power to allow the data in the cache to be written to the non-volatile memory, ensuring no data is lost. In some SSDs that use multi-level cell (MLC) flash memory, a potential issue known as "lower page corruption" can occur if power is lost while programming an upper page. This can result in previously written data becoming corrupted. To address this, some high-end SSDs incorporate supercapacitors to ensure all data can be safely written during

2223-493: The event of power loss, preventing data corruption or loss. Similarly, ULLtraDIMM devices use components designed for DIMM modules, but only use flash memory, similar to a DRAM SSD. DRAM-based SSDs are often used for tasks where data must be accessed at high speeds with low latency, such as in high-performance computing or certain server environments. 3D XPoint is a type of non-volatile memory technology developed by Intel and Micron, announced in 2015. It operates by changing

2280-423: The event of power loss, whether intentional (computer reboot or shutdown) or accidental (power failure or system crash). This is, in general, a weakness (the data must periodically be backed up to a persistent-storage medium to avoid loss), but is sometimes desirable: for example, when working with a decrypted copy of an encrypted file, or using the RAM drive to store the system's temporary files . In many cases,

2337-467: The failure of a single chip may result in the loss of all data stored on it. Nonetheless, studies indicate that SSDs are generally reliable, often exceed their manufacturer-stated lifespan and having lower failure rates than HDDs. However, studies also note that SSDs experience higher rates of uncorrectable errors, which can lead to data loss, compared to HDDs. The endurance of an SSD is typically listed on its datasheet in one of two forms: For example,

RAM drive - Misplaced Pages Continue

2394-536: The feature through the life of Mac OS 9 . Mac OS X users can use the hdid , newfs (or newfs hfs ) and mount utilities to create, format and mount a RAM drive. A RAM drive innovation introduced in 1986 but made generally available in 1987 by Perry Kivolowitz for AmigaOS was the ability of the RAM drive to survive most crashes and reboots. Called the ASDG Recoverable Ram Disk, the device survived reboots by allocating memory dynamically in

2451-467: The first dedicated RAM drives were released in 1983-1985. An early example of a hardware RAM drive was introduced by Assimilation Process in 1986 for the Macintosh. Called the "Excalibur", it was an external 2MB RAM drive, and retailed for between $ 599 and $ 699 US. With the RAM capacity expandable in 1MB increments, its internal battery was said to be effective for between 6 and 8 hours, and, unusual for

2508-500: The information to a particular position before reading or writing can occur. RAM drives can access data with only the address, eliminating this latency . Second, the maximum throughput of a RAM drive is limited by the speed of the RAM, the data bus , and the CPU of the computer. Other forms of storage media are further limited by the speed of the storage bus, such as IDE (PATA), SATA , USB or FireWire . Compounding this limitation

2565-485: The lifespan of the drive. Lower-end SSDs often use QLC or TLC memory, while higher-end drives for enterprise or performance-critical applications may use MLC or SLC. In addition to the flat (planar) NAND structure, many SSDs now use 3D NAND (or V-NAND), where memory cells are stacked vertically, increasing storage density while improving performance and reducing costs. Some SSDs use volatile DRAM instead of NAND flash, offering very high-speed data access but requiring

2622-553: The number of bits stored per cell, ranging from high-performing single-level cells (SLC) to more affordable but slower quad-level cells (QLC). In addition to flash-based SSDs, other technologies such as 3D XPoint offer faster speeds and higher endurance through different data storage mechanisms. Unlike traditional hard disk drives (HDDs), SSDs have no moving parts, allowing them to deliver faster data access speeds, reduced latency, increased resistance to physical shock, lower power consumption, and silent operation. Often interfaced to

2679-741: The performance characteristics such as rotational latency and seek time . As SSDs do not need to spin or seek to locate data, they are vastly superior to HDDs in such tests. However, SSDs have challenges with mixed reads and writes, and their performance may degrade over time. Therefore, SSD testing typically looks at when the full drive is first used, as the new and empty drive may have much better write performance than it would show after only weeks of use. The reliability of both HDDs and SSDs varies greatly among models. Some field failure rates indicate that SSDs are significantly more reliable than HDDs. However, SSDs are sensitive to sudden power interruption, sometimes resulting in aborted writes or even cases of

2736-554: The performance of frequently-accessed data. Traditional interfaces (e.g. SATA and SAS ) and standard HDD form factors allow such SSDs to be used as drop-in replacements for HDDs in computers and other devices. Newer form factors such as mSATA , M.2 , U.2 , NF1 / M.3 / NGSFF , XFM Express ( Crossover Flash Memory , form factor XT2) and EDSFF and higher speed interfaces such as NVM Express (NVMe) over PCI Express (PCIe) can further increase performance over HDD performance. Traditional HDD benchmarks tend to focus on

2793-498: The physical connector and the signaling methods used to communicate between the SSD and the host system. This interface is managed by the SSD's controller and is often similar to those found in traditional hard disk drives (HDDs). Common interfaces include: SSDs may support various logical interfaces, which define the command sets used by operating systems to communicate with the SSD. Two common logical interfaces include: Cramfs The compressed ROM/RAM file system (or cramfs )

2850-431: The reverse order of default memory allocation (a feature supported by the underlying OS) so as to reduce memory fragmentation. A "super-block" was written with a unique signature which could be located in memory upon reboot. The super-block, and all other RRD disk "blocks" maintained check sums to enable the invalidation of the disk if corruption was detected. At first, the ASDG RRD was locked to ASDG memory boards and used as

2907-543: The same location on the disk surface as the original file, whereas in SSDs the new copy will often be written to different NAND cells for the purpose of wear leveling . The wear-leveling algorithms are complex and difficult to test exhaustively. As a result, one major cause of data loss in SSDs is firmware bugs. While both memory cards and most SSDs use flash memory, they have very different characteristics, including power consumption, performance, size, and reliability. Originally, solid state drives were shaped and mounted in

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2964-638: The storage system would, and can be managed in a number of forms, such as a distributed key-value database and a distributed file system . On supercomputers, this layer is typically referred to as burst buffer . Flash-based solid-state drives can be used to create network appliances from general-purpose personal computer hardware. A write protected flash drive containing the operating system and application software can substitute for larger, less reliable disk drives or CD-ROMs. Appliances built this way can provide an inexpensive alternative to expensive router and firewall hardware. SSDs based on an SD card with

3021-655: The time, it was connected via the Macintosh floppy disk port. In 2002, Cenatek produced the Rocket Drive , max 4 GB, which had four DIMM slots for PC133 memory, with up to a maximum of four gigabytes of storage. At the time, common desktop computers used 64 to 128 megabytes of PC100 or PC133 memory. The one gigabyte PC133 modules (the largest available at the time) cost approximately $ 1,300 (equivalent to $ 2,202 in 2023). A fully outfitted Rocket Drive with four GB of storage would have cost $ 5,600 (equivalent to $ 9,486 in 2023). In 2005, Gigabyte Technology produced

3078-679: The use of a battery backup. Thereafter the data can be recovered back in to RAM once power is restored. A host power loss triggers the DDRdrive X1 to back up volatile data to on-board non-volatile storage. Solid-state drive A solid-state drive ( SSD ) is a type of solid-state storage device that uses integrated circuits to store data persistently . It is sometimes called semiconductor storage device , solid-state device , or solid-state disk . SSDs rely on non-volatile memory, typically NAND flash , to store data in memory cells. The performance and endurance of SSDs vary depending on

3135-685: Was discontinued in Windows 7. DR-DOS and the DR family of multi-user operating systems also came with a RAM disk named VDISK.SYS. In Multiuser DOS , the RAM disk defaults to the drive letter M: (for memory drive). AmigaOS has had a built in RAM drive since the release of version 1.1 in 1985 and still has it in AmigaOS 4.1 (2010). Apple Computer added the functionality to the Apple Macintosh with System 7 's Memory control panel in 1991, and kept

3192-609: Was invented and written by Jerry Karlin in the UK in 1979/80. The software, known as the Silicon Disk System , was further developed into a commercial product and marketed by JK Systems Research which became Microcosm Research Ltd when the company was joined by Peter Cheesewright of Microcosm Ltd . The idea was to enable the early microcomputers to use more RAM than the CPU could directly address. Making bank-switched RAM behave like

3249-409: Was made obsolete by squashfs , but the file system got rehabilitated in 2017 for use in low-memory devices where using squashfs may not be viable. Files on cramfs file systems are zlib -compressed one page at a time to allow random read access. The metadata is not compressed, but is expressed in a terse representation that is more space-efficient than conventional file systems. The file system

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