Load Balancing Hosted Services like Exchange OWA

Are there cost effective ways to do load balancing for SMBs?

Specifically.. consider an SMB with Microsoft Exchange. The SMB has multiple ISP's for redundancy (we will say cable and DSL for this example).

So all email flows as well as OWA access over the cable internet. Should the cable internet connection be disrupted, services fail over to using the DSL. The firewall is already configured to handle this from a communication standpoint. And the MX records are configured for both connections with different MX priorities so mail flow works fine.

What is the best way to handle the DNS change/failover for mail.company.com once it fails over to the DSL?

We have looked at some appliances like the Barracuda Load Balancer but they are not cheap. (I know it is all relative). Outside of using dynamic DNS, are there any other cost-effective ways to accomplish this?
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Schuyler DorseyAsked:
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Adam FarageEnterprise ArchCommented:
Without an appliance, the only thing I could think of is either..

1) manual failover, or a separate namespace in the event of a failover
2) manual DNS transfer

Some firewall / load balancing devices do allow for public IP address changes (e.g: if Link 1 fails, follow up with Link 2) but those can get pretty pricey.
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Schuyler DorseyAuthor Commented:
Are there any virtual appliances that you know of?
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Adam FarageEnterprise ArchCommented:
Honestly, no. Sorry pal.
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David Johnson, CD, MVPOwnerCommented:
since the MX record has the priorities it will go to the fail over public ip address,  so the mail will come in and internal cleints will not see any change. you are concerned with external clients accessing the mail? Then a DNS change will have to occur and external clients will update after the TTL has expired.  It will be a manual process without something to do the changes for you..
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kevinhsiehCommented:
This is easy. use DNS Made Easy for your public DNS and they can monitor your OWA server on the cable connection and if that isn't available fail over the A record to the IP address on the DSL. U use them for this exact purpose and it works great. They even send me email when there is a DNS failover.
http://www.dnsmadeeasy.com/services/dns-failover-system-monitoring/
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ChrisCommented:
you can get Virtual Kemp Load Balancers for a few thousand - i think £2K ish these are very effective ways of load balancing both cost and technology wise
http://kemptechnologies.com/uk/loadmaster-family-virtual-server-load-balancers-application-delivery-controllers
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Simon Butler (Sembee)ConsultantCommented:
All of the load balancing providers have virtual versions of their products, the cost is a little less, but still pretty high for an SMB. Kemp and JetNexus are the usual tools of choice here.

Open Source - Zen is the only one I know of, I ran it for 12 months or so and it was ok. It did the job, but its actual failover performance wasn't fantastic and I haven't deployed it outside of my home lab.

The DNS made easy solution is probably the most effective, although you can do something pretty similar with dynamic DNS services.

Simon.
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SteveCommented:
use a failover DNS. they're cheap and don't require any hardware on your site.
Easydns.com is one example I've used but there are many DNS providers that can offer failover.

you can either move your domain reg to them or keep your current domain reg and just use them as a  nameserver. anyone trying to resolve the external FQDN will be given only the IP of a working connection and would be quickly redirected to the other IP if one failed.
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