Secondary storage is nonvolatile memory used to store programs and data between runs.
Four major kinds of secondary storage are summarized below.
Optical disks and magnetic tapes are phased out because they are slow.
In addition, the former have a small capacity and the latter do not permit random access of data.
Hard Disks
Disks are much slower than DRAMs: disks typically take 5-20 milliseconds, while DRAMs take 50-70 nanoseconds—making DRAM about 100,000 times faster.
Yet disks have much lower costs than DRAM for the same storage capacity.
In 2024, the cost per gigabyte of disk is about 30 to 100 times less expensive than DRAM.
Flash Memory
Flash-based removable memory cards typically attach to a USB connection andare often used to transfer files.
The latency of flash memory is 100 to 1,000 times faster than disk, but the cost per GB in 2024 is about twice higher than disk.
External Hard Drives
An external hard drive is another way to back up files, and it allows you to store more than your computer’s limited internal hard drive. An external hard drive connects to the computer with a cable, such as a USB. Regularly save files onto your external hard drive in case your internal hard drive is compromised or damaged.
Cloud Storage
It is the remote use or access of the storage on the Internet.
Cloud storage could be hosted by a shared pool of storage such as networks, servers, and data centers.
By using cloud storage, the data can be entered and updated fast and conveniently.
In addition, data backup is not necessary.