Host-it™ DNS Failover Hosting
WHAT IS Host-it™ DNS FAIL OVER?
DNS Failover monitors your server and if unavailable for a certain period of time will dynamically update your DNS records accordingly so that your domain name points to an available server instead.
This allows you to have a backup site in a separate data centre which can automatically be allocated to your domain if the server you host your web site on is unavailable.
Typically the software is configured to check every three minutes (to allow for reboots) and send an email warning and then after a second check three minutes later change the DNS records automatically. However this setting can be changed to anything between one and sixty minutes.
NB: If your web site writes data to a back end data base it would not be wise to link the backup site to an exact copy of your primary site otherwise the data will become out of sync (the same would apply for email) however rather than showing a blank page this will allow you to have either a maintenance page or for your developers to design a static/basic version of your site which can be viewable if your primary site is unavailable.
Note that if you wish real-time replication of data to give full failover for mission critical solutions we can also offer this via dedicated servers however the cost will be substantially more so the above is a more basic version of this but still useful to have in place as a backup.
WHAT DOES Host-it™ DNS FAILOVER CHECK FOR?
It will check for almost all types of TCP/IP service for example web site and email availability (I.e. HTTP, SMTP, IMAP, POP3, FTP, etc).
Note that unlike our application availability monitoring this will not check that an individual web page is working only that the server itself is responding to the port you select to check (I.e. the entire server/service is down).
HOW DOES IT WORK?
Availability is checked every two minutes and in the event that your primary server is unavailable for X minutes it will send an instruction to your DNS servers (subject to your DNS provider allowing this) to update the IP address to the backup address you nominate. This is done either via the DNS protocol (and can utilise encrypted signatures for security if required) or via WMI or via HTTP dynamic updates.
The failover server will also send you email notifications to notify you of any unavailability.
Note that our price also includes use of our own DNS servers if you wish (recommended).
WILL THE FAIL OVER WORK INSTANTLY AND ALSO FOR ALL USERS?
Part of the set up involves reducing the TTL (Time to Live) on the domains name servers down to five minutes. Although TTL can be reduced to 2 minutes this is the minimum recommended time to ensure that providers who honour the normal TTL minimums do not ignore the entire request.
When you access a web site you use a resolver to convert the DNS into a target IP address for your site. If no user has accessed your site within the period of your TTL from this resolver* then as soon as the fail over server changes the IP for your site the backup site will be viewable. If someone that uses the same resolver* has just accessed your site it may take them up to ten minutes to view the backup site but after this period the backup site will automatically be viewable.
Once service is restored our fail over server will automatically detect that the server is back up and reverse the process.
* This is dependent on your provider honouring lower TTL settings (most do) and those that do not normally have a minimum of two hours.
IS THIS A PERFECT/SEAMLESS SOLUTION?
No. This is a very useful addition to have for peace of mind, however it does have limitations in that the failover will not be seamless and the failback will take the same time. It also means that services of a dynamic nature will also have to have separate replication/failover/failback functionality if you wish to failover to live services so it is more suitable to services or websites which can run independently.
The following scenarios are examples of the best use fo this technology.
1. Important static sites.
2. Automatic back up maintenance page or basic/static site for a dynamic primary site.
3. Back up SMTP site so that if your SMTP gateway is down users can be automatically routed to a backup gateway within a matter of minutes so they can continue to send emails.
WHAT ELSE IS NEEDED?
You will also need to sign up for hosting at the back up location. We can offer this either in our own primary Northampton data centres or if already hosted with us either in Bletchley, Manchester or in the US at a discount to our normal plans with reduced bandwidth).
HOW MUCH DOES THE DNS FAILOVER SERVICE COST?
£75 + vat set up and £2 +vat per month for the first domain and 0.50p + vat for any additional domains.
HOW DO WE ORDER THIS?
As this solution is mostly custom set up please contact us.