Mirroring two servers

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Hello,

I'm about to start a new project and there is a hosting issue that has been discussed about mirroring the servers and having some backup.

A different team is proposing a mirroring option that has server A with one hosting provider and server B with another provider. They are working on a solution that will detect when server A is down so it can redirect to server B.

At first glance I'm not sure that's possible. At least what I think I know is that both servers would need to be within the same network or else, how can one domain work for two different DNS.

I've been doing some research and so far have come empty handed and was wondering if someone here could have some other input regarding this issue we are facing.

Thanks!

Posted 14-Aug-13 4:25am

AAGC15

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AAGC15 · Answer 1 · 2013-08-14T04:35:00

Solution 2

You are right.

It would need to have at least a 3rd "hardware" (some sort of load balancer) to redirect if server A is down.

Our main "concern" is the fact that server A is with one provider and server B is what another provider. I don't know if that is possible or not.

Posted 14-Aug-13 4:35am

AAGC15

Comments

Sergey Alexandrovich Kryukov 14-Aug-13 10:52am

That's correct, but there are simpler uses of mirrors, please see Solution 1.
—SA

Sergey Alexandrovich Kryukov 14-Aug-13 12:59pm

Actually, load balancer is not quite it. It balances physical hosts for the same site, same domain. Mirror is something completely different.
—SA

**Joezer BH** · Answer 2 · 2013-08-14T04:40:00

Solution 3

It can be done via a single front end Load Balancing Server and Back End server possibly remote with proxy servers in the middle like using MS ISA-Server (or its new name Microsoft Forefront Threat Management Gateway).

But - I am not sure this is within your scope...

* If you want, I can provide further reading directions

Cheers,
Edo

Posted 14-Aug-13 4:40am

Joezer BH

v2

Comments

Sergey Alexandrovich Kryukov 14-Aug-13 10:53am

That's correct, but there are simpler uses of mirrors, please see Solution 1.
Actually, this is more about understanding of the purpose of the mirror.
—SA

Sergey Alexandrovich Kryukov 14-Aug-13 12:59pm

Actually, load balancer is not quite it. It balances physical hosts for the same site, same domain. Mirror is something completely different.
—SA

Joezer BH 15-Aug-13 1:52am

It might or might not be it... I can't really say with so little info.
If the two servers operate the same site, then a load balancer will definitely to the job.
If the sites are different but when one is down his users of that site should settle for the second site for vital operations, then a load balancer will not do.

Sergey Alexandrovich Kryukov 15-Aug-13 7:31am

Agreed.
—SA

AAGC15 · Answer 3 · 2013-08-14T06:55:00

Well, I'll try to clarify it a little bit more. (even for me)

Server A (SA) will be with hosting provider A (HPA).
Server B (SB) will be with hosting provider B (HPB).

Each server has the website and the database installed. SA is supposed to be the primary server and SB would just be there as a backup.

First, there should be some sort of process that is updating the database in SB.

So, when, and if, SA goes down, people entering the site should be redirected to SB, that it has, or should have, the database updated, so for visitors this redirection is "transparent".

Our question is if that idea of how it should work can be done through proxys, or load balancers, or just through DNS settings (the domain pointing to several IPs from different servers).

Sergey Alexandrovich Kryukov · Answer 4 · 2013-08-14T04:30:00

It is impossible in the following sense: when server A redirects to server B, server A should still be up.

I don't think such things can be the exact purpose of mirror services. If you explain your purpose properly (perhaps to yourself, too), you will get a change for more constructive answer.

[EDIT]

This is not really about programming or something (so, practically, this is off-topic). This is just understanding of the purpose and site support.

I can tell you some examples of the reasonable way of using mirrors.

Say, you need to perform maintenance work. If you do it on working site, your intermediate steps can break the site integrity. Instead, you fist redirect the whole site A to the mirror B. What is redirection? One line in .htaccess, or something equivalent. You do it and then perform the work: modify the site, perform internal testing.

Then you remove redirection. The you redirect B to A, copy content of A to be, remove redirection. You are done.

Another, trivial reason to have mirrors: you simply inform the readers where the mirrors are. Some other sites, C, D, E, F, 3rd-parties, who supports indices of resource on your fields of activity, will list your sites and indicate that one mirrors another one. The user clicks on one or another link.

—SA