可不可以說一下備份儲存設備的

演進
磁->光學->半導體

影響
應用層面的增加
流動性的增加


特色
磁: 磁碟機, 軟磁碟(機),
磁碟機 - 連媒體一起真空密封
HD<>HDD (HDs are sealed inside the metal case)
光學: 媒體

半導體: USB flash drive快閃記憶, flash card快閃記憶卡, SSD Solid State Disk (max.32GB in Jan.07)
快閃記憶卡 四大類 e.g.
1. SD Secure Digital, miniSD, microSD / Transflash; MMC;
2.CF Compact Flash;
3. MS Memory Stick /Duo /pro;
4. SM Smart Media;
5. XD…and others

優點
磁: 傳輸速度高、容量最大
光學: 普及、每單位成本最平
半導體: 耐碰, 小, 輕, 純電子=>access time最少


**建議你用表格來比較這三大類的優、缺點

數據原理
(English)
Technologies, devices and media
Magnetic storage
Magnetic storage uses different patterns of magnetization on a magnetically coated surface to store information. Magnetic storage is non-volatile. The information is accessed using one or more read/write heads. Since the read/write head only covers a part of the surface, magnetic storage is sequential access and must seek, cycle or both. In modern computers, the magnetic surface will take these forms:
Magnetic disk Floppy disk, used for off-line storageHard disk, used for secondary storageMagnetic tape, used for tertiary and off-line storage
Semiconductor storage
Semiconductor memory uses semiconductor-based integrated circuits to store information. A semiconductor memory chip may contain millions of tiny transistors or capacitors. Both volatile and non-volatile forms of semiconductor memory exist. In modern computers, primary storage almost exclusively consists of dynamic volatile semiconductor memory or dynamic random access memory. Since the turn of the century, a type of non-volatile semiconductor memory known as flash memory has steadily gained share as off-line storage for home computers. Non-volatile semiconductor memory is also used for secondary storage in various advanced electronic devices and specialized computers.
Optical disc storage Optical disc storage uses tiny pits etched on the surface of a circular disc to store information, and reads this information by illuminating the surface with a laser diode and observing the reflection. Optical disc storage is non-volatile and sequential access. The following forms are currently in common use:
CD, CD-ROM, DVD: Read only storage, used for mass distribution of digital information (music, video, computer programs)CD-R, DVD-R, DVD+R: Write once storage, used for tertiary and off-line storageCD-RW, DVD-RW, DVD+RW, DVD-RAM: Slow write, fast read storage, used for tertiary and off-line storageBlu-rayHD DVD The following form have also been proposed:
HVDPhase-change Dual Magneto-optical disc storage
The information is read optically and written by combining magnetic and optical methods
e.g. LS-120, ZIP, Jazz, SparQ…


ref. URL:
http://en.wikipedia.org/wiki/Computer_data_storage#Technologies.2C_devices_and_media

原理 I will not answer
磁帶 is outdated
CD優點 easy to read and use in different computer
CD缺點 capacity too small,you may have to use 20 to 30 of them and file bigger than 700MB can not be backup,hard to rewrite,easy to lost and damaged
DVD優點 bigger in capacity
DVD缺點 seven format so some of them can&#39;t be easy do,hard to rewrite
External Harddisk is good,I suggest this
Good:Big,easy to delete file,USB can be use every where
Bad:Expensive and it may be damage(But if you fall it onto the floor,not a big problem if not in use,but if in use or it is wet,might you things)