I was reading about disk cache. When i googled disk cache, the first result appears is

Blockquote A disk cache is a mechanism for improving the time it takes to read from or write to a hard disk. Today, the disk cache is usually included as part of the hard disk. A disk cache can also be a specified portion of random access memory (RAM). Blockquote

It is not very clear, where exactly the disk cache resides.

  1. Can disk cache reside on hard disk too? If yes, how does it speed up the access times?

  2. Can disk cache reside on both RAM & hard disk both?

  3. Is it the same "cache" that "free" command prints? (for the portion of disk cache that resides on RAM)

  • 3. there are 2 independent disk cache. a) page cache in kernel memory b) disk cache in hdd box itself (but not on disk, it's also RAM) – Ipor Sircer Aug 25 '16 at 14:40
  • If you are talking about single spindle disk that you can buy from any parts store, the cache you are talking abouit resides in a portion of system RAM. In advanced disks, the on-board electronics on the disk spindle itself, has its own cache but handling of that cache is totally up to the disk manufacturer. If you are talking about SAN provided disks, it take a totally different path which is quite long to explain here and is different from one manufacturer to the other. – MelBurslan Aug 25 '16 at 14:47

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