regarding the umount of the nfs fs i stoped the server in LB first so no requests were being made when i did the "remount"

Output from a server with the nfs fs mounted for +-2 days
vmstat -s -S M | egrep 'mem|swap'
3766 M total memory
897 M used memory
237 M active memory
428 M inactive memory
2868 M free memory
199 M buffer memory
452 M swap cache
1999 M total swap
0 M used swap
1999 M free swap
0 pages swapped in
0 pages swapped out

Output from a server with the nfs fs mounted for +-6 days
vmstat -s -S M | egrep 'mem|swap'
3767 M total memory
1863 M used memory
355 M active memory
941 M inactive memory
1904 M free memory
197 M buffer memory
1080 M swap cache
1999 M total swap
0 M used swap
1999 M free swap
0 pages swapped in
0 pages swapped out

Other server with +-7 days with the nfs fs mounted
vmstat -s -S M | egrep 'mem|swap'
3767 M total memory
1830 M used memory
376 M active memory
888 M inactive memory
1936 M free memory
204 M buffer memory
1050 M swap cache
1999 M total swap
4 M used swap
1995 M free swap
532 pages swapped in
1285 pages swapped out


i can see an increase of inactive memory and swap cache and in this last one some swap activity.

Code:

sync && echo 3 > /proc/sys/vm/drop_caches

solved the issue, this means that it back to the normal state.

Before:
free -m
total used free shared buffers cached
Mem: 3767 1865 1902 0 197 1079
-/+ buffers/cache: 588 3178
Swap: 1999 0 1999


After:
free -m
total used free shared buffers cached
Mem: 3767 186 3580 0 4 21
-/+ buffers/cache: 160 3606
Swap: 1999 0 1999


I m confused, the free -m command in second line i was thinking the used field would be really used memory since free (in that line) is already a sum of free + buffers + cache (from the first line)

Can you give some lights? for example if a program requests memory and the free (2º line) is 0 what will happen?

And client caching in a nfs fs ins't dangerous?

thanks