SSD aur HDD dono hi digital data ko store krne ke liye bani hai. Dono mein hi 128GB se leke 20TB tak ki storage capacity hoti hai.
HDD yani hard disk drive, ismai do main components hote hai, spinning platter aur actuator. Spinning platter ek choti si CD ke jesi hoti hai ho jo bhot tezzi se ghumti hai. Isko platter kehte hai, iske andar chote chote sector bane hote hai jinme data store ho jata hai. Jo ek magnetic material se cover hota hai.
Actuator arm ek reader ki tarah kaam karta hai jo platter ke upar laga hota hai, bilkul ek purane record player ki tarah. Jab platter ghoomta hai, to yeh arm data ko read ya write karta hai. HDDs mein data ko fixed-size sectors mein store kiya jata hai, aur yeh sectors baar-baar rewrite kiye ja sakte hain bina kisi issue ke. Matlab purane data, new data se easily replace ho jata hai. HDD ke data transfer krne ki speed thodi slow hoti hai.
SSD, yani solid state drive, ki baat karein to ismein data store karne ke liye ek grid hota hai jo electrical cells se bana hota hai. Yeh grid alag-alag sections mein banti hai jise “pages” bolte hain, aur yeh pages milke group banate hain jise “blocks” kehte hain. SSD ko “solid-state” isliye bolte hain kyunki ismein koi moving parts nahi hote. Sab kuch ek jagah par fixed hota hai.
SSD ka data likhne ka tarika thoda different hota hai. Jab bhi SSD ko data likhna hota hai, toh vo ek controller ke madad se data ko read aur write krti hai. Isme data ko sirf khali pages pe hi likha ja sakta hai. Matlab, ek baar jab ek page pe data likh diya jata hai, us page ko directly overwrite nahi kar sakte.
Isme new data dalne ke liye purane data ko delete krna padta hai. SSDs ki transfer speed HDD se kaafi tez hoti hai, ye badi files ko kaafi easily aur kam time mein transfer kar sakti hai.
History
Solid state drives (SSDs) ki shuruat 1950s mein hui thi, jab do similar technologies, magnetic core memory aur card capacitor read-only store (CCROS), develop hui thi. Yeh auxiliary memory units tab vacuum-tube computers ke dauraan ubhar kar aayi thi, lekin jab saste drum storage units aaye, inka istemal band ho gaya.
1970s aur 1980s mein, SSDs ko semiconductor memory mein implement kiya gaya tha, jaise early IBM, Amdahl, aur Cray supercomputers mein, lekin yeh bahut mehngi thi, isliye inka istemal bahut kam hua. Late 1970s mein, General Instruments ne electrically alterable ROM (EAROM) produce kiya, jo kuch had tak baad mein aane wale NAND flash memory ki tarah kaam karta tha, lekin iski life sirf 10 saal thi, isliye bahut saari companies ne is technology ko chhod diya.
1976 mein Dataram ne Bulk Core launch kiya, jo 2 MB tak ki solid state storage provide karta tha, jo Digital Equipment Corporation (DEC) aur Data General (DG) computers ke liye compatible tha. 1978 mein Texas Memory Systems ne 16 kilobyte RAM solid-state drive introduce kiya, jo oil companies ke liye seismic data acquisition mein istemal hota tha. Agle saal, StorageTek ne pehla RAM solid-state drive develop kiya.
Sharp PC-5000, jo 1983 mein aaya, ne 128 KB solid-state storage cartridges ka istemal kiya jo bubble memory par based thi. 1984 mein Tallgrass Technologies Corporation ne ek tape backup unit launch kiya jisme 40 MB ki storage thi aur ek built-in solid state 20 MB unit bhi tha, jo hard drive ki jagah istemal kiya ja sakta tha. September 1986 mein, Santa Clara Systems ne BatRam introduce kiya, jo 4 MB mass storage system tha aur 4 MB memory modules ke saath 20 MB tak expandable tha. Is package mein ek rechargeable battery thi jo memory chip content ko power off hone par bhi preserve karti thi.
1987 mein EMC Corporation (EMC) ne SSD market mein entry ki, mini-computer market ke liye drives introduce karke. Lekin 1993 tak EMC ne SSD market ko chhod diya.
Aaj bhi, software-based RAM disks 2009 tak istemal hote rahe hain, kyunki yeh doosri technology ke mukable ek order of magnitude zyada fast hain, lekin inka istemal zyada CPU resources leta hai aur per-gigabyte cost bhi zyada hoti hai.
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