Cache vs Buffer: Clear Visual Guide to Their Core Differences

This is the most intuitive visual explanation of the difference between Cache and Buffer I have ever seen.

Question: Cache and Buffer are both caches; what is the main difference?

These two English words should first be examined for their literal meanings; although abstract, they have concrete applications in many contexts.

Typical Buffer example:

The large spring‑like device at the end of a train track acts as a buffer, absorbing impact when a train fails to stop fully, thereby reducing danger.

Typical Cache example:

The illustrated "Food Cache" is a storage box placed in a forest for emergency supplies, functioning like a cache that keeps needed items readily accessible.

In short, the core purpose of a Buffer is to smooth and absorb shocks. For example, writing to a disk 100 times per second creates heavy load; using a buffer to batch writes reduces the frequency and improves efficiency.

The core purpose of a Cache is to speed up data retrieval. When a complex computation result is needed repeatedly, storing it in a cache allows instant reuse without recomputation.

If you pay attention to storage systems, you’ll notice distinct names: write‑buffer and read‑cache, clearly separating their roles.

In practice, the terms are sometimes used interchangeably. Many systems, such as memcached, serve both read and write purposes, and CPU L2/L3 caches are also read‑write.

Using a cache as a buffer is feasible if you can control eviction logic; using a buffer as a cache is limited to special cases where access order is predictable.

Supplement 1: Do not assume Buffer is only for writes and Cache only for reads. Buffers can be used for reading in batch processes, and caches can be used for writing when write patterns are highly random.

Supplement 2: Neither Cache nor Buffer must reside in memory; they can exist on any relatively fast medium, such as a hard drive. For instance, pre‑compiled shaders stored on disk act as a cache, and NTFS uses a logging buffer on disk.

Source: https://urlify.cn/Ibiu2a (Author: 沈万马)