Buffer cache activity can be seen using sar -b (or mpsar -b for SMP):
23:59:44 bread/s lread/s %rcache bwrit/s lwrit/s %wcache pread/s pwrit/s 23:59:49 38 723 95 4 16 75 0 0 23:59:54 38 1280 97 4 22 81 0 0 23:59:59 37 1100 97 2 25 91 0 0 Average 37 1006 96 3 20 83 0 0The buffer cache read hit rate,
%rcache, indicates the percentage by volume of data read from disk (or any block device) where the data was already in the buffer cache.
The buffer cache write hit rate,
%wcache, indicates the percentage by volume of data written to
disk (or any block device) where the block in which the data was to be
written was already in the buffer cache.
%wcacheare also equal to the percentage of read and write requests satisfied using the buffer cache.
bread/s indicates the average
number of kilobytes per second read from the
block devices (including disk drives) into the
the buffer cache.
bwrit/s indicates the average number of kilobytes
per second written from the buffer cache to block devices by the
buffer flushing daemon,