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Web Server




     We had to reboot the web server around 12:15 PM PST today because of an
NFS hang condition between the web server and the main NFS server that holds
the web pages.

     Somewhat technical information follows...

     While I haven't been able to find much regarding the root causes of this
problem, I have observed that when it happens there have been problems with
lost UDP packets happening simultaneously.

     I have found some kernel tweaks that hopefully will reduce or eliminate
this problem by increasing the size of some buffers that are being overrun
when this happens.

     The issue was exacerbated by spammers working out of China that have
software that does not appear to cache DNS entries but instead queries our
server for each attempted delivery and they attempt several thousand times per
minute so it results in a lot of UDP traffic.  I had previously blocked these
people last sunday but they changed IP addresses and were at it again today (to
different addresses in the same class C).

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