Hard Drives & SSDs: Hard Drive Cache

Created on: April 25, 2013
Last updated: August 25, 2015

The Cache in a modern hard drive (or HDD) acts as a type of buffer between the CPU and the mechnical parts inside the hard drive. The buffer is needed because the CPU is far more efficient at moving data than the drive is. By adding onboard cache (which uses chips similar to those in your computer's main memory or RAM), recently used data from the hard drive's spinning magnetic platters can be stored for rapid retrieval by other system components. Put simply, the cache can move the data to the CPU and other internal components much more quickly than the hard drive mechanism can by itself, helping to reduce a common performance "bottleneck". 

Some hard drives offer as much as 256MB of cache to store and feed recently accessed data and related data, although 32MB and 64MB caches are more common.