FreeBSD 9.3 hang on medium load

[ongbenghui]

Hi,

I have an old 1U server running FreeBSD 9.3 that I recently upgraded from 8.4. It is running qmail, dovecot, Apache, etc. Pretty much, light load.

Recently, I am putting up some ffmpeg, and the box will mysteriously "hang". The box is in a remote DC that I don't have direct serial console attached, but it will respond to ping. It will not respond to any telnet or SSH. I thought it must have lost TCP connection, and I set up a cron script to reboot it every hour while troubleshooting. But to my surprise, even cron stops running when it "hangs".

Any advise on any area that I should look at? Or what is the best way to pull out logs during such trouble?

 

[diizzy]

/var/log/messages might have a clue, also look for crash dumps.
Posting dmesg might also help
//Danne

 

[ongbenghui]

Unfortunately, there isn't any crash dumps. /var/log/messages is empty during the period of "hang".

 

[gkontos]

Even if /var/log/messages is empty during that period, it is a good start. dmesg also since we have no idea about your system specs. It would also help if we knew how do you invoke ffmpeg and the output of top before the system hangs.