In our case it was not Cache that was misbehaving, we had a Tomcat application that consumed the memory.
We adjusted /proc/sys/vm/swappiness to 30 (and fixed the tomcat appication and tomcat memory settings) and have not had a repeat of the problem.
Hi,
We experienced this problem in the past when our system ran out of memory. The operating system automatically teminated the heaviest process to free up sufficient resource. The process it selected was the write daemon.
Check /var/log/messages for messages such as
kernel: Out of memory: Kill process 17959 (cache) score 325 or sacrifice child
kernel: Killed process 17959 (cache) total-vm:247757228kB, anon-rss:128kB, file-rss:32kB, shmem-rss:142117896kB
Cache(ENSEMBLE)[17868]: Daemon WRTDMN (pid 17959) died. Freezing system
If you find these, read up about the operating systems implementaion of "oom-killer"