AGiallelis/What is the difference between Disk Cache , Memory Cache, Browser Cache ?

## What is the difference between Disk Cache , Memory Cache, Browser Cache ?
In general, a cache is a "more local" copy of a memory resource that you want to access.
Its a copy that is faster to access than the original, but that memory is also more expensive.

This link, provides some measurements that illustrate the benefits: http://norvig.com/21-days.html#answers

Disk cache is RAM memory, that contains a copy of the information on the disk.
Typically, when you access something on the drive, the whole page is brought into cache, on the assumption that the next access will be in that page.
The first disk seek might take 8ms, while seeks from cache 100 ns  (many times faster - note nanoseconds instead of milliseconds)

Memory cache is the same concept, but the cache is located on the CPU chip.  So the original memory access is 100ns, the L1 cache access can be 0.5 ns.

Browser cache is similar, but stores resources like images, javascript files, etc. on your hard-drive instead of the web page.
Once you access a website, these static resources are stored locally in the browser cache for quicker access the second time you need it.
Using the data from the link above, your access to an image on the web might take 150ms initially, but the second time only 8ms.

Memory and Disk cache implementations will try to guess what you need to use next, while browser caches keep a local copy in case you need to use it again.
	In general, a cache is a "more local" copy of a memory resource that you want to access.
	Its a copy that is faster to access than the original, but that memory is also more expensive.

	This link, provides some measurements that illustrate the benefits: http://norvig.com/21-days.html#answers

	Disk cache is RAM memory, that contains a copy of the information on the disk.
	Typically, when you access something on the drive, the whole page is brought into cache, on the assumption that the next access will be in that page.
	The first disk seek might take 8ms, while seeks from cache 100 ns (many times faster - note nanoseconds instead of milliseconds)

	Memory cache is the same concept, but the cache is located on the CPU chip. So the original memory access is 100ns, the L1 cache access can be 0.5 ns.

	Browser cache is similar, but stores resources like images, javascript files, etc. on your hard-drive instead of the web page.
	Once you access a website, these static resources are stored locally in the browser cache for quicker access the second time you need it.
	Using the data from the link above, your access to an image on the web might take 150ms initially, but the second time only 8ms.

	Memory and Disk cache implementations will try to guess what you need to use next, while browser caches keep a local copy in case you need to use it again.