How to migrate your domain with zero down time and data loss

I have come across several domain migration issues in Web hosting industry. The common issues are the high down time of around 12 – 48 hours experienced while domain transfer and also the data lost during the migration process. In this article I am focusing on how to achieve domain migration with zero down time and also to avoid the data loss. The article is valid for domains hosted under cPanel Linux servers.


Following are the pre-migration checks that are to be performed:

# Connectivity of both the servers
Make sure that both the servers can be connected via SSH, also public keys of the servers are added each other.

#Compatibility of application’s version and modules installed
All the applications and modules installed in the destination server should be compatible with the source server.

#Reseller account and addon domain
Check whether the domain chosen for migration is an addon domain or a reseller account.

#Dedicated IP
Make sure that the dedicated IP is available in the destination server.

#SSL certificate
Copy the SSL certificate, if it is being used by the site.

Steps for domain migration:

 

1. Reduce the TTL value

The major problem that you might face in domain migration is the DNS caching problem. When a remote DNS resolver will make a query to one authoritative DNS server and if the query is successful it will cache that response for a predefined time. This time is so called TTL value. This means that for that amount of time the particular server will use its cached information and no longer query the authoritative server for any additional requests.

 

In order to avoid this problem, bring down the TTL value to 150 seconds and reload rndc, 24 hours prior to migration. This can be done by changing the TTL value in the zone file of the domain. If the domain has addon domains, make sure that the TTL values in their zone files are also brought down. Thus zero down time can be achieved instead of a high value of 24 – 48 hours.

 

2. Migrate the domain to the new server

Migrate the domain using the option “copy multiple accounts/packages from another server” in WHM. Use express transfer option which automatically changes the nameservers and IP address to the new server, so that, even if the query goes to the old server, it will be redirected to the new server.

 

3. Re-sync the databases, mails and contents of the website

To make sure that zero data loss is achieved in data transfer, re-sync the databases and mails. If the website is dynamic, open tables will be present, so there are chances for the data to get corrupted. In order to avoid this situation, contents of the site and databases are synced.

 

4. Make sure that the website is loading well

Make sure that the website is loading well and the mails are received correctly.

 

5. Remove the redirection links in the .htaccess file

Remember to remove the redirection links in the .htaccess file of the new server, that is used to redirect to the new server from the old server.

 

6.After migration, change the IP address for the nameservers

After domain migration, change the nameservers for the domain to that of the new server once the domain starts digging from the new server. Otherwise the domain will depend on two servers for serving. You can again increase the TTL value of the site to the original value after everything is propogating from the new IP.

 

The above is a very rough outline on domain migration with zero down time and zero data loss . If you have any questions, we would be happy to talk to you! 🙂


About the Author :

Greeshma S Giri works as a Jr.Software Engineer in Bobcares. She joined Bobcares in May 2012. She loves reading books and listening to music in her free time.


 

 

 

 


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