In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general the term is uses as large in relation to contemporaneous disk drives, but it has been used large in relation to RAM as for example with floppy disks.
Devices and/or systems that have been described as mass storage include tape libraries, RAID systems, and a variety of computer drives such as hard disk drives, magnetic tape drives, magneto-optical disc drives, optical disc drives, memory cards, and solid-state drives. It also includes experimental forms like holographic memory. Mass storage includes devices with removable and non-removable media.[1][2] It does not include random access memory (RAM).
The USB mass storage device class (also known as USB MSC or UMS) is a set of computing communications protocols, specifically a USB Device Class, defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol set. Specifications: Interface: USB 3.0 Support Devices: IDE & SATA I/II/III, SSDs, Hard Drives, CD/DVD/Blu-ray Drives Drive Size: 2.5' & 3.5' & 5.25' LED Indicators: 1 x IDE; 1 x SATA; 1 x USB; 1 x Power System Requirements: Microsoft Windows XP, Vista, 7, 8.1, 10 (32 or 64 bit) Mac OS X v10.6 and Up Linux OS USB 3.0 or 2.0 Equipped System For USB. The Best NAS (Network Attached Storage) Devices for 2020. Networked storage is the most versatile storage, but that's just one of the many benefits of buying a NAS device. Also, the best NAS devices allow you to use an external drive as a backup. Whether this is an extra precaution or because you want to take the data with you, it’s a useful feature.
There are two broad classes of mass storage: local data in devices such as smartphones or computers, and enterprise servers and data centers for the cloud. For local storage, SSDs are on the way to replacing HDDs. Considering the mobile segment from phones to notebooks, the majority of systems today is based on NAND Flash. As for Enterprise and data centers, storage tiers have established using a mix of SSD and HDD. [3]
Definition[edit]
The notion of 'large' amounts of data is of course highly dependent on the time frame and the market segment, as storage device capacity has increased by many orders of magnitude since the beginnings of computer technology in the late 1940s and continues to grow; however, in any time frame, common mass storage devices have tended to be much larger and at the same time much slower than common realizations of contemporaneous primary storage technology.
Papers[4][5][6] at the 1966 Fall Joint Computer Conference[7] (FJCC) used the term mass storage for devices substantially larger than contemporaneous hard disk drives. Similarly, a 1972 analysis identified mass storage systems from Ampex (Terabit Memory) using video tape, Precision Industries (Unicon 690-212) using lasers and International Video (IVC-1000) using video tape[8] and states 'In the literature, the most common definition of mass storage capacity is a trillion bits.'.[9] The first IEEE conference on mass storage was held in 1974[10] and at that time identified mass storage as 'capacity on the order of 1012 bits' (1 gigabyte).[11] In the mid-1970s IBM used the term to in the name of the IBM 3850 Mass Storage System, which provided virtual disks backed up by Helical scan magnetic tape cartridges, slower than disk drives but with a capacity larger than was affordable with disks.[12] The term mass storage was used in the PC marketplace for devices, such as floppy disk drives, far smaller than devices that were not[a] considered mass storage in the mainframe marketplace.
Mass storage devices are characterized by:
- Sustainable transfer speed
- Cost
- Capacity
Storage media[edit]
Magnetic disks are the predominant storage media in personal computers. Optical discs, however, are almost exclusively used in the large-scale distribution of retail software, music and movies because of the cost and manufacturing efficiency of the molding process used to produce DVD and compact discs and the nearly-universal presence of reader drives in personal computers and consumer appliances.[13]Flash memory (in particular, NAND flash) has an established and growing niche as a replacement for magnetic hard disks in high performance enterprise computing installations due to its robustness stemming from its lack of moving parts, and its inherently much lower latency when compared to conventional magnetic hard drive solutions. Flash memory has also long been popular as removable storage such as USB sticks, where it de facto makes up the market. This is because it scales better cost-wise in lower capacity ranges, as well as its durability. It has also made its way onto laptops in the form of SSDs, sharing similar reasons with enterprise computing: Namely, markedly high degrees of resistance to physical impact, which is again, due to the lack of moving parts, as well as a performance increase over conventional magnetic hard disks and markedly reduced weight and power consumption. Flash has also made its way onto cell phones.[14][15]
The design of computer architectures and operating systems are often dictated by the mass storage and bus technology of their time.[16]
Usage[edit]
External Mass Storage Devices Include
Mass storage devices used in desktop and most server computers typically have their data organized in a file system. The choice of file system is often important in maximizing the performance of the device: general purpose file systems (such as NTFS and HFS, for example) tend to do poorly on slow-seeking optical storage such as compact discs.
Some relational databases can also be deployed on mass storage devices without an intermediate file system or storage manager. Oracle and MySQL, for example, can store table data directly on raw block devices.
Toby fox sans. On removable media, archive formats (such as tar archives on magnetic tape, which pack file data end-to-end) are sometimes used instead of file systems because they are more portable and simpler to stream.
On embedded computers, it is common to memory map the contents of a mass storage device (usually ROM or flash memory) so that its contents can be traversed as in-memory data structures or executed directly by programs.
See also[edit]
- Data storage for general overview of storage methods
- Computer data storage for storage methods specific to computing field
- Disk storage for both magnetic and optical recording of disks
- Computer data storage for storage methods specific to computing field
Notes[edit]
- ^E.g., the obsolete 1956 IBM 350 stored 5 million six-bit characters, larger than contemporary 1.44 and 2.88 MB floppies.
References[edit]
- ^'Definition of: mass storage'. PC Magazine. Ziff Davis. Archived from the original on 2016-07-05. Retrieved 2019-10-10.
- ^Sterling, Thomas; Anderson, Matthew; Brodowicz, Maciej (2018). '17 – Mass storage'. High performance computing. Morgan Kaufmann (Elsevier). ISBN978-0-12-420158-3.
- ^https://www.hyperstone.com/en/NAND-Flash-is-displacing-hard-disk-drives-1249,12728.html, NAND Flash is displacing Hard Disk Drives, Retrieved 29. May 2018
- ^1966FJCC, pp. 711-742, TECHNOLOGIES AND SYSTEMS FOR ULTRA-HIGH CAPACITY STORAGE. sfn error: no target: CITEREF1966FJCC (help)
- ^1966FJCC, pp. 711-716, UNICON Computer Mass Memory System, C.H.BECKER. sfn error: no target: CITEREF1966FJCC (help)
- ^1966FJCC, pp. 735-742, A Photo-Digital Mass Storage System, J. D. KUEHLER, H. R. KERBY. sfn error: no target: CITEREF1966FJCC (help)
- ^1966 Fall Joint Computer Conference. AFIPS Conference Proceedings. Vol. 29. Spartan Books. ISBN978-1-4503-7893-2. 1966FJCC.
- ^Norman F. Schneidewind; Gordon H. Syms; Thomas L. Grainger; Robert J. Carden (July 1972). A SURVEY AND ANALYSIS OF HIGH DENSITY MASS STORAGE DEVICES AND SYSTEMS (Report). US Navy Postgraduate School, Monterey CA. CiteSeerX10.1.1.859.1517. NPS-55SS72071A. Retrieved December 3, 2020.
- ^NPS-55SS72071A, p. 6, A. Definition and Uses of Mass Storage.
- ^The 35th conference was held in 2019.
- ^Bacon, G. C. (October 1974). 'Mass Storage Workshop Report'. Computer. IEEE. 7 (10): 64–65. doi:10.1109/MC.1974.6323336. S2CID29301138. Retrieved December 3, 2020.
- ^Introduction to the IBM 3850 Mass Storage System (MSS)(PDF) (Second ed.). IBM. November 1974. GA32-0028-1.
- ^Taylor, Jim. 'DVD FAQ'. Archived from the original on 2009-08-22. Retrieved 2007-07-08.
In 2003, six years after introduction, there were over 250 million DVD playback devices worldwide, counting DVD players, DVD PCs, and DVD game consoles.
- ^Gonsalves, Antone (23 May 2007). 'Micron predicts flash memory will replace disk drives'. EETimes..
- ^Heingartner, Douglas (2005-02-17). 'Flash Drives: Always on the Go, Without Moving Parts'. New York Times. Retrieved 2008-02-24..
- ^Patterson, Dave (June 2003). 'A Conversation With Jim Gray'. ACM Queue. 1 (4). Archived from the original(– Scholar search) on April 21, 2005.. (A discussion of recent trends in mass storage.)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Mass_storage&oldid=1011735049'
USB flash drives typically implement the USB mass storage device class.
The USB mass storage device class (also known as USB MSC or UMS) is a set of computing communications protocols, specifically a USB Device Class, defined by the USB Implementers Forum that makes a USB device accessible to a host computing device and enables file transfers between the host and the USB device. To a host, the USB device acts as an external hard drive; the protocol set interfaces with a number of storage devices.
Uses[edit]
An action camera being accessed via mass storage device class
Devices connected to computers via this standard include:
- External magnetic hard drives
- External optical drives, including CD and DVD reader and writer drives
- Portable flash memorydevices
- Adapters between standard flash memory cards and USB connections
- Digital audio and portable media players
Devices supporting this standard are known as MSC (Mass Storage Class) devices. While MSC is the original abbreviation, UMS (Universal Mass Storage) has also come into common use.
Operating system support[edit]
Most mainstream operating systems include support for USB mass storage devices; support on older systems is usually available through patches.
Microsoft Windows[edit]
Microsoft Windows has supported MSC since Windows 2000. There is no support for USB supplied by Microsoft in Windows before Windows 95 and Windows NT 4.0. Windows 95 OSR2.1, an update to the operating system, featured limited support for USB. During that time no generic USB mass-storage driver was produced by Microsoft (including for Windows 98), and a device-specific driver was needed for each type of USB storage device. Third-party, freeware drivers became available for Windows 98 and Windows 98SE, and third-party drivers are also available for Windows NT 4.0. Windows 2000 has support (via a generic driver) for standard USB mass-storage devices; Windows Me and all later Windows versions also include support.
Windows Mobile supports accessing most USB mass-storage devices formatted with FAT on devices with USB Host. However, portable devices typically cannot provide enough power for hard-drive disk enclosures (a 2.5-inch (64 mm) hard drive typically requires the maximum 2.5 W in the USB specification) without a self-powered USB hub. A Windows Mobile device cannot display its file system as a mass-storage device unless the device implementer adds that functionality. However, third-party applications add MSC emulation to most WM devices (commercial Softick CardExport and free WM5torage). Only memory cards (not internal-storage memory) can generally be exported, due to file-systems issues; see device access, below.
The AutoRun feature of Windows worked on all removable media, allowing USB storage devices to become a portal for computer viruses. Beginning with Windows 7, Microsoft limited AutoRun to CD and DVD drives, updating previous Windows versions.[1]
MS-DOS[edit]
Neither MS-DOS nor most compatible operating systems included support for USB. Third-party generic drivers, such as Duse, USBASPI and DOSUSB, are available to support USB mass-storage devices. FreeDOS supports USB mass storage as an Advanced SCSI Programming Interface (ASPI) interface.
Classic Mac OS and macOS[edit]
Apple Computer's Mac OS 9 and macOS support USB mass storage; Mac OS 8.5.1 supported USB mass storage through an optional driver.
![Device Device](https://dash.coolsmartphone.com/wp-content/uploads/2015/03/samsung-128gb-storage.jpg)
Linux[edit]
The Linux kernel has supported USB mass-storage devices since its 2.4 series (2001), and a backport to kernel 2.2.18[2] has been made. In Linux, more features exist in addition to the generic drivers for USB mass-storage device class devices, including quirks, bug fixes and additional functionality for devices and controllers (vendor-enabled functions such as ATA command pass-through for ATA-USB bridges, which is useful for S.M.A.R.T. or temperature monitoring, controlling the spin-up and spin-down of hard disk drives, and other options). This includes a certain portion of Android-based devices, through support of USB-OTG, since Android uses the Linux kernel.
Other Unix-related systems[edit]
Solaris has supported devices since its version 2.8 (1998), NetBSD since its version 1.5 (2000), FreeBSD since its version 4.0 (2000) and OpenBSD since its version 2.7 (2000). Digital UNIX (later known as Tru64 UNIX), has supported USB and USB mass-storage devices since its version 4.0E (1998). AIX has supported USB mass-storage devices since its 5.3 T9 and 6.1 T3 versions; however, it is not well-supported and lacks features such as partitioning and general blocking.[3]
External Mass Storage Devices Examples
Game consoles and embedded devices[edit]
The Xbox 360 and PlayStation 3 support most mass-storage devices for the data transfer of media such as pictures and music. As of April 2010, the Xbox 360 (a) used a mass-storage device for saved games[4] and the PS3 allowed transfers between devices on a mass-storage device. Independent developers have released drivers for the TI-84 Plus and TI-84 Plus Silver Edition to access USB mass-storage devices.[5] In these calculators, the usb8x driver supports the msd8x user-interface application.
Device access[edit]
USB card readers typically implement the USB mass storage device class.
The USB mass-storage specification provides an interface to a number of industry-standard command sets, allowing a device to disclose its subclass. In practice, there is little support for specifying a command set via its subclass; most drivers only support the SCSI transparent command set, designating their subset of the SCSI command set with their SCSI Peripheral Device Type (PDT). Virtual piano offline. Subclass codes specify the following command sets:
- Reduced Block Commands (RBC)
- SFF-8020i, MMC-2 (used by ATAPI-style CD and DVD drives)
- QIC-157 (tape drives)
- Uniform Floppy Interface (UFI)
- SFF-8070i (used by ARMD-style devices)
- SCSI transparent command set (use 'inquiry' to obtain the PDT)
The specification does not require a particular file system on conforming devices. Based on the specified command set and any subset, it provides a means to read and write sectors of data (similar to the low-level interface used to access a hard drive). Operating systems may treat a USB mass-storage device like a hard drive; users may partition it in any format (such as MBR and GPT), and format it with any file system.
Because of its relative simplicity, the most-common file system on embedded devices such as USB flash drives, cameras, or digital audio players is Microsoft's FAT or FAT32 file system (with optional support for long filenames). Large, USB-based hard disks may be formatted with NTFS, which (except for Windows) is less supported. However, a keydrive or other device may be formatted with another file system (HFS Plus on an Apple Macintosh, or Ext2 on Linux, or Unix File System on Solaris or BSD). This choice may limit (or prevent) access to a device's contents by equipment using a different operating system. OS-dependent storage options include LVM, partition tables and software encryption.
In cameras, MP3 players and similar devices which must access a file system independent of an external host, the FAT32 file system is preferred by manufacturers. All such devices halt their file-system (dismount) before making it available to a host operating system to prevent file-system corruption or other damage (although it is theoretically possible for both devices to use read-only mode or a cluster file system). Some devices have a write-protection switch (or option) allowing them to be used in read-only mode; this makes files available for shared use without the risk of virus infection.
Two main partitioning schemes are used by vendors of pre-formatted devices. One puts the file system (usually FAT32) directly on the device without partitioning, making it start from sector 0 without additional boot sectors, headers or partitions. The other uses a DOS partition table (and MBR code), with one partition spanning the entire device. This partition is often aligned to a high power of two of the sectors (such as 1 or 2 MB), common in solid state drives for performance and durability. Some devices with embedded storage resembling a USB mass-storage device (such as MP3 players with a USB port) will report a damaged (or missing) file system if they are reformatted with a different file system. However, most default-partition devices may be repartitioned (by reducing the first partition and file system) with additional partitions. Such devices will use the first partition for their own operations; after connecting to the host system, all partitions are available.
Devices connected by a single USB port may function as multiple USB devices, one of which is a USB mass-storage device. This simplifies distribution and access to drivers and documentation, primarily for the Microsoft Windows and Mac OS X operating systems. Such drivers are required to make full use of the device, usually because it does not fit a standard USB class or has additional functionality. An embedded USB mass-storage device makes it possible to install additional drivers without CD-ROM disks, floppies or Internet access to a vendor website; this is important, since many modern systems are supplied without optical or floppy drives. Internet access may be unavailable because the device provides network access (wireless, GSM or Ethernet cards). The embedded USB mass storage is usually made permanently read-only by the vendor, preventing accidental corruption and use for other purposes (although it may be updated with proprietary protocols when performing a firmware upgrade). Advantages of this method of distribution are lower cost, simplified installation and ensuring driver portability.
Design[edit]
Some advanced hard disk drive commands, such as Tagged Command Queuing and Native Command Queuing (which may increase performance), ATA Secure Erase (which allows all data on the drive to be securely erased) and S.M.A.R.T. (accessing indicators of drive reliability) exist as extensions to low-level drive command sets such as SCSI, ATA and ATAPI. These features may not work when the drives are placed in a disk enclosure that supports a USB mass-storage interface. Some USB mass-storage interfaces are generic, providing basic read-write commands; although that works well for basic data transfers with devices containing hard drives, there is no simple way to send advanced, device-specific commands to such USB mass-storage devices (though, devices may create their own communication protocols over a standard USB control interface). The USB Attached SCSI (UAS) protocol, introduced in USB 3.0, fixes several of these issues, including command queuing, command pipes for hardware requiring them, and power management.
Specific USB 2.0 chipsets had proprietary methods of achieving SCSI pass-through, which could be used to read S.M.A.R.T. data from drives using tools such as smartctl (using the -d option followed by 'chipset').[6] More recent USB storage chipsets support the SCSI / ATA Translation (SAT) as a generic protocol for interacting with ATA (and SATA) devices.[7] Using esoteric ATA or SCSI pass-through commands (such as secure-erase or password protection) when a drive is connected via a USB bridge may cause drive failure, especially with the hdparm utility.[8]
See also[edit]
References[edit]
- ^'Changes in Windows to Meet Changes in Threat Landscape'. TechNet Blogs. 2009-04-28. Retrieved 2012-11-07.
- ^'Driver for USB Mass Storage compliant devices'. Archived from the original on 2005-09-23.
- ^'eserver: HOWTO: JFS2 on USB device on AIX 5.3.11.1'. Eserver.livejournal.com. 2010-01-21. Archived from the original on 2012-03-31. Retrieved 2012-11-07.
- ^'Xbox Live's Major Nelson » USB Memory Support for the Xbox 360 coming April 6th :'. Majornelson.com. 2010-03-26. Retrieved 2012-11-07.
- ^'83Plus:Software:usb8x/Asm Interface/MSD'. WikiTI. 2009-02-18. Retrieved 2012-11-07.
- ^'#25 (SCSI pass through for SMART via USB on MacOSX smartmontools? 3rd party code available!) – smartmontools'. Sourceforge.net. Retrieved 2014-01-21.
- ^'USB smartmontools'. Sourceforge.net. Archived from the original on 2012-02-07. Retrieved 2014-01-21.
- ^'ATA Secure Erase - ata Wiki'. Ata.wiki.kernel.org. 2013-07-22. Retrieved 2014-01-21.
Further reading[edit]
From the USB Implementers Forum website:
External links[edit]
- What actually happens when you plug in a USB device? – Linux kernel internals
Retrieved from 'https://en.wikipedia.org/w/index.php?title=USB_mass_storage_device_class&oldid=995254424'