How is data retained in persistent storage?

Data is retained in persistent storage by being written onto non-volatile storage devices like hard drives, SSDs, or flash drives.

In more detail, persistent storage refers to any data storage device that retains data after power to the system is shut off. This is in contrast to volatile memory, such as RAM, which loses any stored information when the power is turned off. Persistent storage devices include hard disk drives (HDDs), solid-state drives (SSDs), flash drives, and optical discs like CDs and DVDs.

Data is retained in these devices through different methods depending on the type of storage. For example, in a hard drive, data is stored magnetically on spinning platters. When data is written to the drive, the read/write head changes the magnetic orientation of specific areas on the platter to represent binary data (1s and 0s). This magnetic orientation remains even when the drive is powered off, allowing the data to be retained.

In a solid-state drive, data is stored in flash memory cells. These cells hold an electrical charge to represent binary data. Unlike the magnetic storage in hard drives, flash memory cells can hold their charge without power, making them non-volatile. This is why SSDs are faster and more reliable than HDDs, but also more expensive.

Flash drives work in a similar way to SSDs, using flash memory to store data. However, they are typically smaller and more portable than SSDs, making them ideal for transporting data between different devices.

Optical discs like CDs and DVDs store data by using a laser to burn pits into a reflective surface. These pits and the spaces between them represent binary data. Once the data is burned onto the disc, it can be read back by a laser even when the disc is not being powered.

In all these cases, the key to data retention in persistent storage is the use of non-volatile storage methods that can maintain data without a constant power supply. This allows data to be stored long-term and accessed whenever needed, making persistent storage a crucial part of any computer system.