Filesystems, Disks and Memory

Hello,

I wanted to share an experience I had today which was quite a learning experience and perhaps useful for others who may run into the issue at some point in the future.


Basically, the scenario involves a OS which was installed on a machine which hardware-wise, had a SATA Drive. The web server Apache for this machine had earlier crashed a website. The machine I could confirm from a remote location was still operational (i.e. responding to ping attempts)

Taking a monitor/keyboard to the location of the server and subsequently plugging in a monitor, I noticed the logs were flooded with messages to the like of:


backlog limit exceeded
backlog limit exceeded
backlog limit exceeded
backlog limit exceeded
backlog limit exceeded
... ... ...



(which maybe points to a hard drive which may be failing.)

Trying next to login, the machine was unresponsive therefore I rebooted.
Next, I was able to console in as root, and noticed that certain log messages were flooding my shell session. They were similiar to the following:


hda failure rewrite_ext
reset succesful
hda failure rewrite_ext
reset succesful
hda failure rewrite_ext
reset succesful
hda failure rewrite_ext
hda failure rewrite_ext
... ... ...


I then had to switch to another console via Ctrl+Alt+F2/F3 to attempt to restart or at least check the status of the Apache service httpd.

I then had more messages which were flooding even my logged in sessions which I had never seen before. (No prompt and no way to enter commands)

____________________


In anycase, I came to the conclusion after searching a bit on google, is that perhaps the backlogs were flooding the hard drive and causing a DoS, which then maybe caused Apache to stop running.

Also searching google, I noticed that certain BIOS settings may contribute to this behavior, as the machine had no IDE drives, only SATA drives yet somehow the settings were entered incorrectly or not changed to "Enhanced" with a particular setting. (AHCI?)

Some of my colleagues thought the hard drive suspect of failing. Just an interesting experience.................... : )