Re: Finding the Bottleneck
I always thought that doing a local lookup would be far faster than doing
one on a remote dns cache. We use bind, and set the forwarders to 2 other
DNS servers that are only lightly loaded and on the same network.
Additionally, as far as I can see, most emails get sent to the same
moderately large list of domains (eg. aol), so the local DNS server
would've cache them already anyway.
----- Original Message -----
From: "Russell Coker" <email@example.com>
To: "Rich Puhek" <firstname.lastname@example.org>; "Jason Lim"
Sent: Friday, June 08, 2001 6:18 PM
Subject: Re: Finding the Bottleneck
On Friday 08 June 2001 05:47, Rich Puhek wrote:
> In addition to checking the disk usage, memory, and the other
> suggestions that have come up on the list, have you looked at DNS?
> Quite often you'll find that DNS lookups are severely limiting the
> performance of something like a mailing list. Make sure that the mail
> server itself isn't running a DNS server. Make sure you've got one or
Why not? When DNS speed is important I ALWAYS install a local DNS.
Requests to 127.0.0.1 have to be faster than any other requests...
> two DNS servers in close proximity to the mail server. Make sure that
> the DNS server process isn't swapping on the DNS servers (for the kind
The output of "top" that he recently posted suggests that nothing is
> with 128 MB of RAM as your DNS server. Also, if possible, I like to
> have the DNS server I'm querying kept free from being the authoratative
> server for any domains (not always practical in a real life situation,
> I know).
How does that help?
If DNS caching is the issue then probably the only place to look for a
solution is djb-dnscache.
http://www.coker.com.au/bonnie++/ Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/ Postal SMTP/POP benchmark
http://www.coker.com.au/projects.html Projects I am working on
http://www.coker.com.au/~russell/ My home page