question: How does a USB or another small storage device keep so much data on it?
comment: **First things first - Binary** So we know electronics run on electricity (we need to plug them in or give them batteries, after all, and it's in the name). If you compare electricity to water flowing through a pipe, voltage is like the water's pressure and current is like the flow rate (how much water is moving through the pipe). Obviously that can't represent something as complex as text or photos or music, so we'll make some kind of code. If you had water coming out of your faucet, and I wanted to send you a message by varying the pressure and volume, it'd be pretty difficult for you to tell the difference between small changes right? Also what if there was a problem with the water supply from the city and we lost a little bit of pressure? We wouldn't be able to get to our full range. But if I said, "Faucet On = 1" and "Faucet Off = 0", you'd be able to tell pretty easily if water is flowing or not. We could then make patterns, and say 010100 = the letter A, or 101100111 = the color blue. & #x200B; **Storage** Ok so we have our code and I'm going to send 3 messages with the faucet and tell you to write them down. In this situation I'm like the PC and you're the USB stick, and our messages are files. Also, you know I'm going to ask you later what I told you to write down, so you'll probably want a way to organize the information I'm giving you so you can read it back to me exactly. & #x200B; So you take your sheet of paper and you draw a grid, like graph paper. You put a small number on each cell, 1, 2, 3, 4. As I turn the water on and off, you mark a 1 in the first grid cell, a 0 in the next, so on and so forth. When I'm done with the first message you make a note that we ended on cell 56, then continue on to the next one and so on. When I ask you for file #2, you look at your notes and jump to cell 57, and read me back the 1's and 0s' & #x200B; **Flash Memory** USB sticks use something called flash memory, it's a chip made from silicone that represents our sheet of paper with the grid lines. Each grid cell can either be filled with a small amount of electricity or not. Flash memory was kind of revolutionary because we don't need a battery or power source to keep that electricity in the cell, that's why you can unplug your usb stick and it's fine, it just holds all of the electrons in place. Using the water analogy, it'd be like if each cell was a small cup and you put a lid on each one that had water. & #x200B; **Size** If you want to store more information in our first scenario, you can either get more pieces of paper, but that will get heavy pretty quickly. So you decide to just draw you grid lines smaller and smaller to fit more cells onto the same sheet. Eventually you probably can't draw lines any closer together, your pen is just too thick, so you need a smaller pen. We've improve this process for computers over the years and can now "draw" these grid lines on the silicone chip RIDICULOUSLY small. We're talking **nanometers**. For perspective, if a nanometer is an inch, the width of a human hair is a mile. We do this with super fancy equiptment and processes to pack a tonnnne of those little cells in there.
passages: Mechanically addressed systems use a contact structure ("head") to read and write on a designated storage medium. Since circuitry layout is not a key factor for data density, the amount of storage is typically much larger than for electrically addressed systems.
   Removable media have become very common with microcomputer platforms. They allow programs and data to be transferred between machines without a physical connection. Common examples include USB flash drives, memory cards, CD-ROMs, and DVDs. Utilities have therefore been developed to detect the presence and availability of a medium and then mount that medium without any user intervention.
   The device is split into two main areas. At the beginning of the device is the metadata section, which consists of a root block, and a generic array of blocks that can be allocated to store metadata. The rest of the device is another contiguous generic array of blocks that can be allocated to store data. The metadata section usually uses a few percent of the device, depending on the size of the device.
   Inside the plastic casing is a small printed circuit board, which has some power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface between the USB connector and the onboard memory, while the other is the flash memory. Drives typically use the USB mass storage device class to communicate with the host.
  
  Section::::Technology.:Flash memory.
   The memory in flash drives is commonly engineered with multi-level cell (MLC) based memory that is good for around 3,000-5,000 program-erase cycles, but some flash drives have single-level cell (SLC) based memory that is good for around 100,000 writes. There is virtually no limit to the number of reads from such flash memory, so a well-worn USB drive may be write-protected to help ensure the life of individual cells. 
   Robotic-access storage devices may have a number of slots, each holding individual media, and usually one or more picking robots that traverse the slots and load media to built-in drives. The arrangement of the slots and picking devices affects performance. Important characteristics of such storage are possible expansion options: adding slots, modules, drives, robots. Tape libraries may have from 10 to more than 100,000 slots, and provide terabytes or petabytes of near-line information. Optical jukeboxes are somewhat smaller solutions, up to 1,000 slots.
   Non-volatile memory retains the stored information even if not constantly supplied with electric power. It is suitable for long-term storage of information. Volatile memory requires constant power to maintain the stored information. The fastest memory technologies are volatile ones, although that is not a universal rule. Since the primary storage is required to be very fast, it predominantly uses volatile memory.
   To provide additional data security, the Centera access nodes, when no read or write operation is in progress, constantly communicate with the storage nodes, checking the presence of at least two copies of each blob as well as their integrity. Additionally, they can be configured to exchange data with a different, e.g. off-site, Centera system, thereby strengthening the precautions against accidental data loss.
   When a content address is provided to the device, it first queries the directory for the physical location of the specified content address. The information is then retrieved from a storage node, and the actual hash of the data recomputed and verified. Once this is complete, the device can supply the requested data to the client. Within the Centera system, each content address actually represents a number of distinct data blobs, as well as optional metadata. Whenever a client adds an additional blob to an existing content block, the system recomputes the content address.
   The development of high-speed serial data interfaces such as USB made semiconductor memory systems with serially accessed storage viable, and the simultaneous development of small, high-speed, low-power microprocessor systems allowed this to be incorporated into extremely compact systems. Serial access requires far fewer electrical connections for the memory chips than does parallel access, which has simplified the manufacture of multi-gigabyte drives.
   BULLET::::- "IEEE Reynold B. Johnson Data Storage Device Technology Award" (with SanDisk co-founders Ei Harari and Jack Yuan) for "leadership in the development and commercialization of Flash electrically erasable programmable read-only memory-based data storage products", 2006.
  
  Section::::Activities.
   Data storage
  
  Data storage is the recording (storing) of information (data) in a storage medium. DNA and RNA, handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Recording is accomplished by virtually any form of energy. Electronic data storage requires electrical power to store and retrieve data. 
   Many of the smallest players are powered by a permanently fitted rechargeable battery, charged from the USB interface. Fancier devices that function as a digital audio player have a USB host port (type A female typically).
  
  Section::::Uses.:Media storage and marketing.
   Flash drives use little power, have no fragile moving parts, and for most capacities are small and light. Data stored on flash drives is impervious to mechanical shock, magnetic fields, scratches and dust. These properties make them suitable for transporting data from place to place and keeping the data readily at hand.
  
  Flash drives also store data densely compared to many removable media. In mid-2009, 256 GB drives became available, with the ability to hold many times more data than a DVD (54 DVDs) or even a Blu-ray disc (10 BDs).
   In practice, flash file systems are used only for memory technology devices (MTDs), which are embedded flash memories that do not have a controller. Removable flash memory cards and USB flash drives have built-in controllers to perform wear leveling and error correction so use of a specific flash file system does not add any benefit.
  
  Section::::Capacity.
  
  Multiple chips are often arrayed to achieve higher capacities for use in consumer electronic devices such as multimedia players or GPSs. The capacity of flash chips generally follows Moore's Law because they are manufactured with many of the same integrated circuits techniques and equipment.
   USB flash drives use the USB mass storage device class standard, supported natively by modern operating systems such as Windows, Linux, and other Unix-like systems, as well as many BIOS boot ROMs. USB drives with USB 2.0 support can store more data and transfer faster than much larger optical disc drives like CD-RW or DVD-RW drives and can be read by many other systems such as the Xbox One, PlayStation 4, DVD players, automobile entertainment systems, and in a number of handheld devices such as smartphones and tablet computers, though the electronically similar SD card is better suited for those devices.
   Section::::Design.
   Traditional hard drives run on mechanical parts, which uses the permanent disk to store your personal data. The hard disk drives usually have a 10 centimeter diameter and are a centimeter thick. These drives use a magnetic recording technique. We, as users, can easily manipulate our data on this medium i.e. add, copy, cut or paste data on it though this technique. The principle of magnetic flux is used for such processes. Basically the hard drive remembers which data is where and how to manipulate the data according to the user’s preference by remembering the flux patterns.
   In NOR gate flash, each cell resembles a standard MOSFET, except the transistor has two gates instead of one. On top is the control gate (CG), as in other MOS transistors, but below this, there is a floating gate (FG) insulated all around by an oxide layer. The FG is interposed between the CG and the MOSFET channel, and because the FG is electrically isolated by its insulating layer, any electrons placed on it are trapped there and, under normal conditions, will not discharge for many years. When current flow through the MOSFET channel binary code is generated, reproducing the stored data.
   A USB flash drive is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than . Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. , flash drives with anywhere from 8 to 256 GB were frequently sold, while 512 GB and 1 TB units were less frequent. As of 2018, 2TB flash drives were the largest available in terms of storage capacity. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances (shelf storage time).
   NAND gate flash utilizes tunnel injection for writing and tunnel release for erasing. NAND flash memory forms the core of the removable USB storage devices known as USB flash drives, as well as most memory card formats available today.
  
  Section::::Memory types.:Magnetic.
   A data packet consists of the PID followed by 0–1,024 bytes of data payload (up to 1,024 bytes for high-speed devices, up to 64 bytes for full-speed devices, and at most eight bytes for low-speed devices), and a 16-bit CRC.
   Section::::Uses.:Power.:Internal disk drives.
  
  In older desktop PCs, PATA (aka "IDE") devices such as 5.25 inch optical drives and 3.5 inch hard drives are typically powered by means of AMP MATE-N-LOCK Y-cables.
  
  Section::::Uses.:Power.:USB.
   For external memory and the USB flash drive, appropriate software, e.g., the Unix command "dd", is needed to make the bit-level copy. Furthermore, USB flash drives with memory protection do not need special hardware and can be connected to any computer. Many USB drives and memory cards have a write-lock switch that can be used to prevent data changes, while making a copy.
   Since the access time depends on the physical location of the data on the device, mechanically addressed systems may not be "random access" as are electrically addressed semiconductor NVRAM. For example, magnetic tape stores data as a sequence of bits on a long tape; transporting the tape past the read/write head is required to access any part of the storage. Tape media can be removed from the drive and stored, giving indefinite capacity at the cost of the time required to retrieve a dismounted tape.
  