Computer Memory and Storage

A failover system is a backup operational mode in which the functions of a primary system component are assumed by secondary system components when the primary system becomes unavailable due to failure.

ROM stands for Read-Only Memory. Its contents are written during manufacture and cannot be altered or erased by normal computer operations, making it non-volatile and read-only.

RAM (Random Access Memory) is a type of primary storage that is fast, relatively expensive per gigabyte, and volatile, meaning it loses its data when power is turned off.

Non-volatile storage is computer memory that can retain stored information even when not powered, meaning it does not lose its contents when power is removed.

A flash memory card (like an SD card or MicroSD card) is very small and thin, can store large amounts of data, and typically requires a card reader to be read by a computer. A flash memory stick (USB drive) has a built-in USB connector and does not require a separate reader.

DVD-R stands for DVD-Recordable, which can be written to only once by the user. DVD-RW and DVD-RAM are rewritable formats, while DVD-ROM is read-only and cannot be written to by the user at all.

Magnetic storage devices, such as hard disk drives and magnetic tapes, save data by magnetizing particles on a spinning disk or tape. Optical devices use lasers, and solid-state devices use electronic circuits.

Solid-state storage devices, such as SSDs and USB flash drives, have no moving parts and store data electronically using flash memory. In contrast, optical and magnetic devices rely on spinning discs or moving heads.

CD-ROM (Compact Disc Read-Only Memory) is commercially manufactured with pre-recorded data and cannot be written to or erased by the user. CD-R and CD-RW are designed for users to write their own data.

RAM (Random Access Memory) is volatile memory, meaning it loses its stored data when the power is turned off. ROM, HDD, and SSD are non-volatile storage media that retain data without power.

Compared to Hard Disk Drives (HDDs), Solid State Drives (SSDs) typically offer smaller maximum storage capacities at comparable price points. SSDs are faster, lighter, and more durable, but HDDs remain more cost-effective for extremely large storage capacities.

A flash drive (flashdisk) is significantly smaller and more pocketable than a portable external Solid State Drive, making portability its primary advantage. Portable SSDs, while also portable, are larger but offer much faster speeds and higher capacities.

VHS tapes use serial (sequential) access, meaning you must fast-forward or rewind through the tape to reach a specific point. CDs, DVDs, and SSDs use direct (random) access, allowing immediate retrieval of data from any location.

A Hard Disk Drive (HDD) uses direct (random) access, allowing the read/write head to jump directly to any location on the disk. Magnetic tape and VHS require serial access, where data must be read sequentially from the beginning.

Serial (or sequential) access requires reading through all preceding data in order to reach a specific target location. Direct access, on the other hand, allows the system to jump directly to the target data.