Re: [PLUG] BIND TTL's & Migrating a site from shared hosting to dedicate

Henry Umansky <henry@humansky.com> · 2005年11月15日 14:34:09 -0500

Changing your TTL is a good step, but there is no guarantee that other 
peoples DNS servers will honor your TTL. Some places increase default 
TTLs to help with performance and lookups. I would recommend having the 
old server still accept incoming connections just forward the connection 
to the new server (this can be done using iptables, iirc). There's just 
a few things to keep in mind, traffic from the old server to new server 
will most likely be unencrypted and vulnerable to MOTM (man in the 
middle) attacks. Also, there will be a network performance bottleneck, 
as you can already see by updating the database to the new server. One 
way to bypass the unencrypted problem is either setting up an SSH tunnel 
or set up a VPN connection. As far as the performance bottleneck, I 
don't thinkn there is much you can do besides wait for the rogue DNS 
servers to update their tables with your new IP address. Just my 0ドル.02.
Henry Umansky
henry@humansky.com
http://www.humansky.com 

Marc Zucchelli wrote:
I have a situation with one of my clients where I
think I will have to move their database driven site
which is on a shared hosting account, to a dedicated
server with another company.
I have done this in the past and there was one

problem. Basically, I copied and installed the site

and the database to the dedicated server, and I

modified the code for the site on the shared server so

that it connects directly to the database that is on

the dedicated server, so that there is one centralized

database during the DNS propogation rather than two. 
For about 48 hours, the site ran extremely slow for

those that were still getting the old site because it

had to wait for db queries that are going to another

network, as opposed to being on the same machine. 
That is the problem I am trying to resolve.
The best solution I can think of is to change the
DNS's TTL's to say 15 minutes a few days before the
move. That way if the site runs slowly for anyone, it
will only be for 15 minutes.
Does that sound like the best solution?
In the bind zone files, the top line is usually:
$TTL 14400
How is this different than the TTL's in the SOA
record? Or the individual TTL's in the individual A,
NS, etc records?
Thanks!

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