It is not easy to produce the problem so I will just write the experienced problems not how it is produced.
1) During login, it shows the last login time and then waits for 3-4 seconds to give shell prompt (considerable)
2) Sometimes the connection window freezes (console is also) not showing any characters pressed; after 4-5 seconds it shows all the characters written. (considerable)
3) Almost every half an hour, while pinging the server it shows Request Timeout then the NFS share drops.
4) CPU is seen as 99 %idle in sar output for the normal times. When the freeze happens the sar output shows 0 %idle, 70 %iowait and 30 %system.
Then the screen freeze and connection drops.
Any recommendation to check where the problem might be? Any ideas?
The login delay probably is because of SSH trying to do an reverse lookup. You can disable that by setting
UseDNS no
in your sshd_config
As for your main problem: if it's occurring periodically, it's probably a cronjob. Check those for anything requiring a lot of memory, as it could be connected to massive swapping.
Thanks pludi,
The line was commented in configuration but I don't know if it is enabled by default. Anyway, after I changed that, it responded normally during login.
For the freezing problem, it doesn't happen periodically. It is hard to generate without knowing where it hangs but the problem seems to be less than before when the update service is stopped.
Edit: After many tries, finally the problem is nfs-related. Whenever a file is imported with script ,which triggers with new added file, the problem occurs. The CPU goes 100% and the timeout messages show up; still the transfer completes.
