MS DNS Server Using Excessive Memory and hanging

Just in case you are using Microsoft DNS Server as a secondary DNS, and installed updates realeased late in December 2007 or early January 2008.

There is a memory leak issue with an update for the DNS server released around that time that causes MS DNS to use excessive memory, as much as several hundred MB. Even worse, at some point the server stops responding to queries. The problem may be difficult to detect as it happens only when there are a lot of secondary zones on the server and secondary DNS server failure may go un-noticed for a while.

To my knowledge, no update has been released by Microsoft so far that fixes this memory leak issue,  so if you are being affected by it, your best workaround for now is probably what some of the other DNS admins are doing: restart the DNS service at a set interval.

On our two secondary MS DNS servers, we are using dnscmd.exe /restart in a batch file scheduled to run every hour. The dnscmd.exe restarts the service (or resets it, to be more precise) very quickly. However, this tool is a part of the 'Windows Server 2003 Support Tools' package, and if you don't have it or want to install it, you can also use Net Stop "DNS Server" and Net Start "DNS Server" commands in a batch file and schedule it to run every hour or so.

In either case, the schduled task must be run with an Administrator privilege to be able to restart the DNS service. 

Since restarting is quick and these are secondary servers, it is not a huge problem. 

Lets hope an update with a fix to this memory issue will be released soon.