Storage is where data lives permanently. Unlike RAM, which loses its contents when power is removed, storage retains data indefinitely. Understanding the main types of storage, what capacity means, and why backup matters is essential for anyone working with data.
Hard Disk Drives (HDD)
A hard disk drive stores data on spinning magnetic platters. A read/write head moves across the platters to access data. HDDs have been the dominant storage technology for decades. They offer large capacities at relatively low cost per gigabyte, but they are slower than solid-state drives and more vulnerable to physical shock because of their moving parts.
Solid-State Drives (SSD)
A solid-state drive stores data in flash memory chips with no moving parts. SSDs are significantly faster than HDDs for both reading and writing data. They are more resistant to physical shock and consume less power. The cost per gigabyte is higher than HDDs, though the gap has narrowed considerably.
NVMe (Non-Volatile Memory Express) is a protocol that allows SSDs to connect directly to the CPU via a high-speed interface, making them faster still than SSDs using older interfaces.
Capacity
Storage capacity is measured in gigabytes (GB) and terabytes (TB). One terabyte is 1,000 gigabytes. To put this in context:
- A typical office document is a few kilobytes to a few megabytes
- A high-resolution photograph is a few megabytes
- A video file can be several gigabytes
- A large database or dataset can be hundreds of gigabytes to multiple terabytes
- AI model weights can range from a few gigabytes to hundreds of gigabytes
The speed of storage affects how quickly data can be read into RAM for processing. Fast NVMe storage can significantly reduce the time needed to load large datasets. For databases and data warehouses, storage speed is a key factor in query performance.
Backup
All storage devices can fail. Hard drives have moving parts that wear out. SSDs have a finite number of write cycles. Data that exists only on one device is at risk. A backup is a copy of data stored separately from the original — on a different device, in a different location, or in cloud storage.
The 3-2-1 backup principle is a widely referenced guideline: keep three copies of data, on two different types of media, with one copy stored off-site. This is a concept, not a rigid rule — the appropriate backup strategy depends on the value of the data and the acceptable level of risk.
- HDD vs SSD difference
- NVMe storage explained
- backup strategy 3-2-1
- storage capacity gigabytes terabytes