2. UtilizationMagnetic energyDevices that store information by means of: hard diskfloppy disk(obsolete), tapeCore memory、Bubble memory(Bubble memory appeared in the 1970s, but failed to achieve commercial success in the 1980s when the price of hard disk dropped sharply.),USB drive
3. Devices that store information optically, such as CDs or DVDs
4. Devices that use magneto-optical method to store information, such as MO（Magneto-optical disk）
5. Use other physical objects such asPaper card, paper tape and other information storage devices such as:Punch card, punching tapeKnotetc.
6. Dedicatedstorage system : for data backup orDisaster recoveryIt is a special information system that uses high-speed network to store large amounts of data.
PD is "phase change rewritableOptical drive(Phase Change Rewritable Optical DiskDrive).
PD disc adoptsphase transitionThe data regeneration principle of optical mode is the same as that of CD, which is based on reflectionAmount of lightThe difference between 1 and 0 identifies the signal.The PD disc is the same shape as the CD disc. It is packed in a box to protect the data on the disc.
PD optical disk system is widely used in computer and workstation environmentsfloppy diskThe hard disk is in the same data structure unit format, and also adopts the 512bit/unit MCAV format that can be used immediately in the computer environment. With this format, reading and writing operations can be carried out at a higher speed than using the CLV format CD － R/CD － RW, and the high-speed search speed is realized.Based on the above advantages, PD has beenWindows95Lead computerOSAnd thanks toATAPIThe standardization of the interface has established itsProduct position。Phase change discIn order to protect the CD, the system uses the method of putting the CD in the protection box, while the CD is used as a bare disk.In order to process PD boxed disks and CD bare disks at the same time, the PD optical disk system adopts a new tray filling method.This mode will also be used on DVD-RAM.
MO（MagnetoOptical）
data recordIs a thermo magnetic process, which is related tomagnetic material OfCurie temperatureIs related to the threshold property ofCurie pointwrite in.During writing, focuslight spotWhen the recording material is heated beyond the Curie point (about 200 ℃) with a small magnetic field (about 300 gauss)Magnetic domainMake a difference.When the material is cooled below the Curie point, the direction of the magnetic domain is fixed.This recording processMaterial propertiesShows a high degree ofRepeatability(More than one million times).
The writing process of traditional MO record information needs three times: the first timeEraseOriginal recorded data: continuously irradiate the medium with a focused laser beam to make its temperature exceed the Curie point. At the same time, apply a magnetic field in one direction, and the medium will be magnetized in the same direction;The data is recorded for the second time. At this time, the opposite magnetic field is applied, and the medium is irradiated by the laser pulse modulated by the recording time, so that the place corresponding to the pulse is magnetized in the direction;The third pass verifies whether the data is written correctly.Each time corresponds to a rotation of the disc.
In the future, direct rewrite (DOW, DirectOverwrite, or OW, Over? Write) technology will be used to combine the first and second pass into one, so that MOAccess speedIt can be replaced in general occasionsHard diskApplication.MO media has become a computing environment. Users can integrate their entire computing system, including operating system, application software and their ownworking paper, mounted on one MO media.From the performance of the MO system, it can run completely on MO without loadingHDDLevel on.This greatly broadens MO'sapplication area 。This also makes MO have stronger technical vitality and market competitiveness.Media technology has enabled the speed, reliability, bitStorage price, rewritable times, archive time, etc.These characteristics enable MO to compete with pureOptical recordingDevice CDRW/DVD-RAMIs in an irreplaceable position in the competition.
mobile hard disk drive(Mobile Hard disk) As its name implies, hard diskstorage medium , a storage product that exchanges large capacity data between computers and emphasizes portability.The vast majority of mobile hard disks in the market are based on standard hard disks, while only a few are based onMicro hard disk(1.8 inch hard disk, etc.), but the price factor determines that the mainstream mobile hard disk is still based on the standardLaptop hard driveIs based on.Because the hard disk is used as the storage medium, the data reading and writing mode of the mobile hard disk is the same as that of the standard IDE hard disk.Most mobile hard disks useUSB、IEEE1394etc.transmission speed Faster interface, which can be carried out with the system at a higher speeddata transmission。As of 2009, the reading speed of mainstream 2.5-inch brand mobile hard disk is about 15-25MB/s, and the writing speed is about 8-15MB/s.
AndFlash MemoryDisk uses Flash Memory as the storage medium. The mobile hard disk is physically a standard hard disk orMicrohard diskAs a storage medium.Therefore, the mobile hard disk'sSeismic capacityNot as good asflash disk, but it can provide more capacity than flash disk.The mobile hard disk needs more power than the flash disk. Sometimes, especially when using the front mountedUSB HubWhen one USB interface cannot provide sufficient power, two USB interfaces need to be used to power it.Because of this, many mobile hard disk products use a three branch data cable, one of which is used to supplement power supply when the power supply is insufficient. There are also some mobile hard disks using low-power notebook hard disks that no longer need a three-way USB cable with auxiliary power supply due to power consumption requirements.For mobile hard disks that use desktop hard disks to connect to hard disk boxes or conversion lines, because the voltage and current used by desktop hard disks are higher than those used by notebook hard disks, external power supply is required.Another WI-FI/Blue tooth wirelessNetwork hard disk, such mobile hard disks can exchange data with personal computers without connecting.
In the past decade, 3.5 inchfloppy diskDriverAlways small andMicrocomputerEssential forExternal memory, but in the face of increasingly largeMultimedia filesAnd toData backupThe traditional 1.44MB floppy disk with small capacity, slow speed and instability is increasingly showing huge limitations.Traditional 1.44Mfloppy diskThe market is shrinking year by year.
High capacity FD is developed on the basis of the original disk.MainlyZip, Supper floppy disk (formerly LS120), HiFD, etc.The development goal of these three large capacity FDs is to replace the current 3.5-inch FDs and strive to occupy the huge floppy disk marketleading role 。domestic marketOn the other hand, zip competes with LS-120.
Zip diskIs 70 times larger than 1.44MB floppy disk. ZipDriverThanks to the adoption ofHard disk headTechnology, thus achieving a speed of 2945 rpm,Average seek time29 ms.Although the speed of ZIP is fast, the biggest problem encountered when using the Zip drive is that the Zip drive cannot read 1.44MB of hundreds of millions of existing cardsfloppy disk。So 3MCompaq、O．R．、Panasonic、MitsubishiandHitachiIn 1996, six other companies introduced the LS-120 floppy disk drive, which has a capacity of 120MB and is compatible with 1.44MB floppy disks.
The Clik disc is only 50.8mm × 50.8mm (2 inches × 2 inches) in size, with a capacity of 40MB, Aimega launched two models for itDriver, one is forNotebook computerOfPCMCIACard drive, which adopts a read/write technology similar to Zip, with a disk speed of 2941r/min,Average seek time29ms, continuous datatransmission speed It has reached 620KB/s, and the QuikSync software equipped for it can automatically translate the importantFile backupOn the Clik disk, it provides real-time protection and management of files;The other is forDigital cameraAppliedSM cardandCF cardReader writer, it can read and write the data in the SM card and CF card into Clik, and then pass the data in Clik through theParallel portIt is transmitted to the computer. The average seek time of this drive is less than 25ms, and the average duration isData transmission rate700KB/s.The CF card hard disk of IBM is a miniature of the conventional hard disk. Its volume is only 50mm × 42.8mm × 36.4mm, its weight is 16g, and its capacity is 170MB and 340MB.It uses standard CF+Interface mode, the disk speed is 4500r/min,Average seek time15 ms, the media data transmission rate is 30.1 Mbps~45.2 Mbps, and the interface data transmission rate is 5.2 MB/s.Its reading and writing speed is no less than that of some traditional hard disks, and its shockproof performance has been greatly improved.
Flash isEPROM(Electrically erasableProgram memory）It uses floating gatetransistorAs a basic storage unit, nonvolatile storage can be realized, and real-time rewriting can be realized without special equipment and methods.Flash memory usesCMOS processCompatible processing technology. Most flash memory uses 0.5mm and 0.35mm processes,SamsungFlash memory with 0.27mm process has been launched, and the 0.25mm process will be realized soon.along withIntegrated circuit processWith the development of technology, the internal circuit density of flash memory is becoming larger and larger, and the number of bytes stored in each transistor is also increasing, thus increasing the capacity of flash memory. Samsung andToshibaIt is planned to launch 1GBNAND Flash 。In recent years, various forms of flash basedstorage deviceThey have sprung up like mushroomsRich and colorful, the size is getting smaller and larger,Interface modeMore and more flexible.
The latest fourth generationFlash card, mainly SanDisk's MultiMedia card, NexcomTechnology's SerialFlash card and Sony's MemoryStickMemory stick。The fourth generation flash memory cards all use serial flash memory chips, which greatly reduce the external pins of the chip. At the same time, because of the serial way of reading and writing data, the power consumption of the chip is also reduced.The MultiMedia card uses a 7-pin interface, with an overall size of 32mm × 24mm × 1.4mm and a maximum capacity of 32MB,Data transmission rate2MB/s, to expand itsScope of applicationSanDisk also introduced a MultiMedia card with parallel port and USB interfaceAdapter, the computer can easily read and write MultiMedia cards.
According to the analysis of storage experts in the IT industry,Data capacityIn the next three years, it will multiply by more than five times.How to use the decreasingBackup timecomeStorage managementA large number of emerging data has become an important part of ITSenior managementImportant topic ahead!As the last moment of 2000 approaches, it is even more urgent for users at all levels to safely and efficiently backup and store large amounts of data.The products used for storage in the market areOptical tower、CD、DVD, MO, hard diskTape driveEtc.Tower, CD, DVD instorage capacity Both of them are technologically advanced products, but their storage capacity is small. For users who need to backup a large amount of data for a long time and need to minimize the cost, tape products are the best choice.fromDevelopment trendFrom the point of view, storage automation has become inevitableBackup deviceIs followingmanual operationConversion to automatic backup device;Another trend is to useNetwork Backup, which can effectively reduceadministration costAnd operating costs, but network backupnetwork techniqueIs still waiting.Therefore, the application of tape drives has practical significance for current users.
CDR/CDRW
Although CD － ROMDriverThe price of CD － R is low, and it has been widely used in the field of computer storage, but its fatal weakness of being unable to write has gradually become an obstacle to its developmentWritable disc。Its characteristics areWrite onlyOnce, CD － R after writingCDIt cannot be overwritten, but it can be overwritten in the CD ROM drive and CD RCD writerWas read more than once on.The biggest advantage of CD-R optical disc is that its recording cost is the lowest among various optical disc storage mediaMegabyteThe cost required is lower thanRMB0.1 yuan, and its service life is very long, so CD-R has gradually becomedata storage The mainstream products ofData exchange, database distributionArchive storageandMultimedia softwarePublishing and other fields have been widely used.Another related successful technology, CD-RW, also reveals that it is aInformation storageSuitable optional products.CR － RW provides a limited number of reading and writing functions.in fact,CD-R/CD-RW has become a cheap and universal tool for desktop system file exchange.Future CD-R/CD-RWIt will develop in the following aspects:
The latest CD － R recorder will support CD － UDF formatDOSOr under Windows, the CD － R recorder has the same independent drive letter or icon as the floppy drive.Users do not need to useBurning software, you can directly read and write to the CD-R recorder just like using a floppy drive, which greatly simplifies the operation and management of the CD-R recorder and brings great convenience to users.
In addition to the three recording modes of whole disc writing, track writing and multi segment writing, the recorder will also support incremental packet writing in the future.
In order to reduce the disk space waste in the process of additional recording, Philips Company has developed the incremental packet writing mode.The biggest advantage of the incremental package recording method is that it allows users to add recording data to a track for many timesData areaThe front and rear gaps of only 7a sectorTherefore, the incremental package recording mode is different from the data of the soft disk and hard diskRecord modesimilar.The incremental package burning mode is especially suitable for applications that often only need to back up a small amount of data.
USB disk, full name "USB interface"mobile hard disk drive”, the English name is "USB removable (mobile) hard disk".The name of USB flash disk comes fromLongcoA new type of storage device produced by the company, called "USB disk", also called "mobile hard disk", is connected by USB interface.After the USB interface is connected to the host computer of the computer, the USB data can be put on the computer.The data on the computer can also be put on the USB stick, which is very convenient.However, the equipment of similar technology produced later can no longer be called "USB flash disk" because of the patent registration of Lucco, but is renamed "USB flash disk" or "flash memory" in the image“flash disc”Etc.Later, the term "U disk" was widely known because it was easy to remember, and the two have also become common, and they are no longer distinguished.Its biggest characteristics are: small and easy to carry, large storage capacity, cheap price.yesportable storage deviceone of.When the USB flash disk first came out, the storage capacity seemed not large, and the price was also quite expensive. For example, the 32M USB flash disk also cost about 300 yuan at that time, and the capacity of 256M USB flash disk was even on the newsCCTVOfnewsHowever, with the innovation and popularization of technology, the capacity and price of USB flash drives have changed dramatically. The general capacity of USB flash drives is 1G, 2G, 4G, 8G, 16G, etc. The price of the most common 4G, for example, is about 55 yuan.The capacity of USB flash drives has been greatly improved, such as 4G, 8G and 16G USB flash drives.It is portable and belongs to mobile storage device, so of course it is not inserted in the chassis. We can hang it on our chest andKey chainAnd even put it in your wallet.
According to different manufacturers and applications, the flash memory card may have SmartMedia（SM card）、Compact Flash（CF card）、PCI-E Flash memory cardMultiMediaCard（MMC card）、Secure Digital（SD card）、Memory Stick（Memory stick）、XD-Picture Card（XD card）AndMicrohard disk(MICRODRIVE) Although these flash cards have different appearances and specifications, their technical principles are the same.
Compact Flash was first introduced by SanDisk in 1994.CF card has PCMCIA-ATAFunction and compatibility with it;The CF card weighs only 14g and is only the size of a cardboard match (43mm x 36mm x m3.3mm). It is a solid product, that is, it has no moving parts when working.CF cardFlash Memory(flash) technology is a stableStorage solutions, no battery is needed to maintain the data stored therein.For the saved data, the CF card is better than the traditionaldisc driveHigher security and protection;The reliability of CF card is 5 to 10 times higher than that of traditional disk drive and type III PC cardPower consumptionOnly 5% of small disk drives.These excellent conditions make most digital cameras choose CF card as their preferred storage medium.
PCI-e flash memory card（PCI-EExpress) is the latest bus andInterface standard, its original name is "3GIO", PCIe belongs to high-speed serial point-to-pointDual channelHigh bandwidth transmission. The connected devices are allocated with exclusive channel bandwidthshared resource, mainly supporting initiativePower management，Error Reporting, end-to-end reliable transmission,Hot plugas well asService quality(QOS) and other functions.PCIePCI-SIG(PCI Special Interest Organization) changed its name to“PCI-Express”, referred to as "PCI-E".This new standard will completely replace the current PCI andAGP, finally realizedBus standardUnification of.It is mainly used in SSDs (solid state drives) in servers. There are many suppliers of PCIe flash cards, such as IBM-TMSIntel、LSI、OCZ, Samsung (planned), SanDisk, STEC, SuperTalent and Toshiba (planned), among which LSI products are the most prominent, with the best quality and performance.The latest version is PCI-E 3.0, and there are also PCI-E (version 1.0) that have not been delisted.The bandwidth of 2.0 is twice that of 1.0, and that of 3.0 is twice that of 2.0, which is 5GHz x 4.PCI Express 2.0The main content of the specification isData transmission speedHas made a major upgrade from the previous 2.5GbpsBus frequencyDouble to 5.0Gbps, which means that the previous PCI Express 2.0 x16 interface can double to an astonishing 10GB/sBus bandwidth（1GB/s=8Gbps）。
The SM (Smart Media) card is created byToshibaThe Flash Memory memory card released in November 1995,SamsungIn 1996, the company purchased the production and sales license, and these two companies became the main manufacturers of SM cards.In order to promote SmartMedia to become an industrial standard, SSFDC (Solid State Floppy Disk Card) was established in April 1996. In fact, SmartMedia was initially called SSFDC, and in June 1996, it was renamed SmartMedia and became Toshiba'sRegistered trademark）。SSFDC Forum has more than 150 members, including many large manufacturers, such as Sony, SharpJVC、Philips、NEC, SanDisk, etc.SmartMedia card is also a common micro memory card in the marketMP3 playerIt is very popular.
Memory StickMemory stick, developed by Sony Corporation, with a size of 50mm x 21.5mm x 2.8mm and a weight of 4g.Delicate and eye-catching blue shell (the new MG is white), and it has a write protection switch.And many Flash MemoryMemory cardDifferent, the Memory Stick specification is not publicStandardization Organization。Adopt Sony's own appearance, protocol, physical format and copyrightProtection technologyTo use its specifications, you must negotiate and sign a license with Sony.Memory Stick also includes the controller, which uses a 10 pin interface,data busIt is serial, the highest frequency can reach 20MHz, the voltage is 2.7V to 3.6V, and the average current is 45mA.It can be seen that this specification is quite similar to the MMC that appeared at about the same time.
XDThe full name of the card is XD-PICTURE CARD, which is made by Fuji andOLYMPUSThe small memory card jointly launched for digital cameras uses a single-sided 18 pin interface, which is the smallest memory card..XD is taken from "Extreme Digital", which means "extreme number".XD card is a relatively new flash card. Compared with other flash cards, it has many advantages and features.PocketOverall dimensionThe overall dimension is 20mm × 25mm × 1.7mm, and the total volume is only 0.85 cubic centimeters, about 2 grams. It is the world's most portable and smallest digital flash memory card.first-classcompatibility, with variouscard reader, can be easily connected to personal computers.Large storage capacity. The theoretical maximum capacity of the XD card can reach 8GB, with a large expansion space.XD cards seen in the market have different capacity specifications such as 16MB, 32MB, 64MB, 128MB, 256MB, etc.
Microhard disk(Microdrive) was originally developed by IBM as a super miniHard disk driveProducts.Its initial capacity is 340MB and 512MB, while the product capacity is 1GB, 2GB and 4GB.Compared with the past, the micro hard disk drive reduces the speed (4200rpm to 3600rpm), which reduces the power consumption but enhances the stability.
（Multimedia Card，MMC card）Is a kind offlash Memory card standard.In 1997, Siemens andSanDiskCo development, technology based on Toshiba'sNANDThe flash memory technology is smaller than the early memory cards based on IntelNOR flash memory technology, such as CF card.MMC card is about the same size as a stamp, about 24mm x 32mm x 1.5mm.
The MMC card originally used a 1-bit serial interface, but newer standards allow simultaneous transmission of 4-bit or 8-bit data.In recent years, MMC card technology has been almost completely replaced by SD card, but since MMC card can still be read by devices compatible with SD card, it still has its role.
MMC cards have a capacity of up to 2 GB and are used on almost all devices using memory cards, such as mobile phonesDigital audioplayer, digital cameras, andPersonal digital assistantMedium.Due to the emergence of Secure Digital, few companies use MMC slots in their devicesPin compatibleMMC card can be used in all supportedSD cardOn the device.However, a few companies, most notablyNOKIAMMC is still fully supported.
stored procedure
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stored procedureIt is a process written by flow control and SQL statements. This process is compiled and optimized and stored indatabase serverMedium,application programWhen using, just call it.In ORACLE, several related processes can be combined to formPackage。
stored procedureIt is a program written in Transact SQL language provided by SQL Server.Transact-SQL LanguageSQL Server provides a language for designing database applications. It is the main program between applications and SQL Server databasesDesign interface。It's likeOraclePL-SQL and Informix'sDatabase system structureInformix - 4GL language in.
