Published: 21 August 2024
Contributors: Phill Powell, Ian Smalley
Primary storage, located on the system board, is the computer component that stores the programs, data and instructions that are in active use by that computer.
Primary storage is also known as main memory. Because of its close proximity to the central processing unit (CPU), it’s simpler to both read and write to primary storage. This allows processors to give faster access to the data and instructions that primary storage holds.
The main or primary memory, also known as internal memory, holds relatively small amounts of data that the computer can access as it operates. External memory, also known as secondary memory, involves storage devices that can house data in an ongoing manner.
Primary storage operates by maintaining the data and instructions in current use by the CPU. To run programs, the CPU reaches out to the primary storage to get needed instructions. Primary storage is responsible for three operational tasks that are essential to computer processing.
When a computer is turned on, it goes through a boot cycle in which necessary components of the operating system get added to the RAM from the computer’s hard disk. Once the OS is loaded, the system is ready to manage operations.
Before applications can be run, they are first loaded from their existing hard disk location into RAM, which orchestrates the running of the app and gives it faster data retrieval than it originally would have exhibited.
It’s not just apps that get loaded into RAM. The same holds for any data that needs to be processed by an application. This distinction covers data from a diverse range of apps, such as those dealing with higher mathematics, rendered images and edited files.
Numerous types of memory dominate the discussion of primary storage:
Random access memory (RAM)
RAM is the most vitally important type of memory. RAM handles and houses numerous key processes, including system apps and those processes the computer is currently managing. It also serves as a kind of launchpad for files or apps.
Read-only memory (ROM)
ROM allows the user to view the data, but it doesn’t allow changes to the collected data. ROM differs from RAM in permanence. ROM is nonvolatile storage because its data remains even when the computer is turned off. One example of ROM is a CD, with contents that are written once and locked in place.
Another example is the basic input/output system (BIOS), a program that monitors hardware functionality when the computer is first powered on before loading the computer’s OS. Because the BIOS is needed every time the computer is turned on, the BIOS is stored in ROM.
Cache memory
Another key form of data storage is cache memory, which stores data that is often retrieved and used. Cache memory contains less storage capacity than RAM, but is faster than RAM.
Registers
The registers, located inside CPUs, provide the fastest data access times and store data for near-instant processing.
Flash memory
Flash memory offers the best of both worlds: speedy access times plus nonvolatile storage that allows data to be written and saved (and to be rewritten and resaved). Flash memory is used in smartphones, digital cameras, USB flash drives and flash drives.
Cloud storage
Under certain circumstances, cloud storage might operate as primary storage. For example, organizations hosting apps in their own data centers need to use some type of cloud service for storage purposes.
Both dynamic random-access memory (DRAM) and static random-access memory (SRAM) are other types of RAM-based semiconductor memory used in data storage, but they are engineered quite differently. DRAM relegates each data bit to a memory cell that contains an extremely small capacitor and transistor, while SRAM uses a latching, flip-flop circuitry to store each data bit.
In terms of volatility, DRAM’s capacitor can hold an electric charge, but not indefinitely. Such an electric charge is subject to leakage over time, so the DRAM combats this loss by having an external memory refresh circuit that routinely rewrites the data in each capacitor and thus helps ensure nonvolatility, making it perfect for secondary storage purposes. Meanwhile, SRAM is quicker than DRAM but loses its data when power is removed from the system.
It’s generally considered that SRAM enables faster processing than DRAM, but because of this attribute, SRAM is also considered to be more expensive to implement than DRAM. Because of its speed, SRAM is typically used in cache memory and registers, while DRAM is most often used to constitute a computer’s main memory.
An incorrect assumption often confuses the issue of primary storage—the classification of a resource as primary storage or related to another level (or tier) of memory is not determined by its storage architecture, size or the amount of storage space it provides. It’s the utility of that particular resource and how the resource is used that drives its memory designation.
This widens our definition of the various types of primary storage possible. Through this utility-based approach, primary storage can take multiple forms. Primary storage might involve the use of storage arrays (data storage hardware) such as hard disk drives (HDDs) or flash-based solid-state drives. Or primary storage might mean the use of a shared storage area network (SAN) or a network attached storage (NAS) array.
Here again, it’s how the resource is going to be used that drives its designation as primary storage or secondary storage. If an organization needs to be able to process high-transaction applications like data management, the speedier SAN platform provides the necessary high performance.
There are several ways to consider the difference between primary storage and secondary storage methods.
Primary storage is to secondary storage as a human being’s short-term memory is to their long-term memory. Just as short-term memory is more focused on the “current” thinking that’s most relevant to a person then, primary storage is more focused on the current processing that the computer is running. Conversely, secondary storage provides long-term storage and is more akin to a person’s long-term memory, which operates with less frequency and might require more mental processing (computer processing) to retrieve long-held memories (long-stored data).
Another easy way to differentiate between the two types of storage is by what happens to each when operating power is removed. Primary storage is volatile, with that data effectively vanishing when the computer powers down. Secondary storage typically uses nonvolatile memory, which retains its ability to store data in a long-term nature, even after power is removed.
Still another basic way to compare primary storage and secondary storage is by their respective system performance. Computer systems that use primary storage exhibit faster access times than systems relying upon secondary storage systems.
Various devices are used to deliver storage solutions, per their level of use and importance:
Primary storage devices
Here are the most commonly used primary storage devices:
- Solid-state drives
- Hard-disk media
Secondary storage devices
Secondary storage devices (SSDs) include:
- Hard disk drives
- Magnetic tapes
- Memory chip/SSD cards
- USB flash drives
- CD, DVD and Blu-Ray discs
Tertiary storage devices
Slotting in just beneath secondary storage devices are devices that deal with tertiary memory, or data in its rawest and most unstructured form. In tertiary storage, automation is used to switch between the removable media (like optical discs and tape reels) that are accessible by the computer through the use of carousels and similar robotic mechanisms. Tertiary storage is not known for lightning-fast processing speeds, but rather for providing unfailingly consistent operation.
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