disk buffer与page cache的不同

, the small amount of buffer memory present on a hard drive.
, the cache of disk pages kept by the operating systems, stored in unused 

Disk buffer

In , disk buffer (often ambiguously called disk cache or cache buffer) is the embedded memory in a acting as a between the rest of the computer and the physical that is used for storage. Modern hard disks come with 8 to 128  of such memory, and solid-state drives come with up to 512 MB or 1 GB of cache memory.

Since the late 1980s, nearly all disks sold have embedded and either an , , , or interface. The drive circuitry usually has a small amount of memory, used to store the bits going to and coming from the disk platter.

The disk buffer is physically distinct from and is used differently from the typically kept by the in the computer's . The disk buffer is controlled by the microcontroller in the , and the page cache is controlled by the computer to which that disk is attached. The disk buffer is usually quite small, from 8 to 64 , and the page cache is generally all unused . While data in the page cache is reused multiple times, the data in the disk buffer is rarely reused.In this sense, the terms disk cache and cache buffer are misnomers; the embedded controller's memory is more appropriately called the disk buffer.

Note that , as opposed to , usually have normal cache memory of around 0.5–8 GiB.

Page cache

In computing, a page cache, often called a ,is a "transparent" of disk-backed pages kept in (RAM) by the for quicker access. A page cache is implemented in with the memory management, and is mostly transparent to applications.

All physical memory that is not directly allocated to applications is usually used by the operating system for the page cache. Since the memory would otherwise be idle and is trivially reclaimed when applications request it, there is generally no associated performance penalty and the operating system might even report such memory as "free".

read speeds are low and require expensive compared to main memory—this is why RAM upgrades usually yield significant improvements in computers' speed and responsiveness.Separate disk caching is provided on the hardware side, by dedicated RAM or chips located either in (inside a hard disk drive; properly called ) or in a . Such memory should not be confused with page cache.