What is the difference between buffer and cache memory in Linux?

Question

To me it's not clear what's the difference between the two Linux memory concepts : buffer and cache. I've read through this post and it seems to me that the difference between them is the expiration policy:

1. buffer's policy is first-in, first-out
2. cache's policy is Least Recently Used.

Am I right?

In particular, I'm looking at the two commands: free and vmstat

james@utopia:~$ vmstat -S M
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
5  0      0    173     67    912    0    0    19    59   75 1087 24  4 71  1
james@utopia:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          2007       1834        172          0         67        914
-/+ buffers/cache:        853       1153
Swap:         2859          0       2859

Answer 1

Buffers are associated with a specific block device, and cover caching of filesystem metadata as well as tracking in-flight pages. The cache only contains parked file data. That is, the buffers remember what's in directories, what file permissions are, and keep track of what memory is being written from or read to for a particular block device. The cache only contains the contents of the files themselves.

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