Live Backup

[tendemo]

Ive two servers that are a replica of each other, howver can one tell me of a software program that can do real time backups so that if one fails the other can take over without any qualms. Thanks

[CVMichael]

Maybe you should look into RAID ?

What do you mean by: "if one fails the other can take over" ?

If you have a backup, you have to recover from the backup in order to get it to work again (for whatever you are doing).

[chris128]

What do you mean by: "if one fails the other can take over" ?

If you have a backup, you have to recover from the backup in order to get it to work again (for whatever you are doing).

Not strictly true, although I doubt the OP is willing to pay for the type of solutions that would do what he is asking for...
Clustering is a technology that allows several servers to be used 'as one' and if one of the servers in the cluster fails then another of the servers will take over its role immediatley, so that there is minimal (if any) noticeable downtime to users trying to access the data on that server. I wont go into the details but it is very expensive.

There is also virtualization - where you would use one or two powerful physical servers to run several 'virtual' servers on each. Using this setup you can do a 'live migration' of one of the virtual servers onto another physical server if the first one were to go down so that within a minute or two it is all up and running again. There are various other ways in which you could use this system to keep a semi live backup but again it is expensive.

On the software side of things, I have heard some people mention an application called "Double Take" (www.doubletake.com) which basically replicates data from one server to another constantly so that you can switch over to the 'spare' server if the live one goes down. Again though, I'm pretty sure it is quite expensive.

So... now we come to the free solution, which is not so much a solution but more of a "I suppose it will have to do, I cant afford the other solutions" situation. Also, this solution is only useful if you are just wanting to replicate files/folders, its not a lot of use for things like exchange server databases or any other such database that is constantly in use. The solution I am talking about is this: You use a free download from Microsoft called "Robocopy" - this little tool is basically an extended version of the XCOPY and COPY commands that are already part of Windows. With Robocopy though, you can specify that it 'mirrors' two locations, so that if a file is deleted from the source location then it is deleted from the target as well etc etc. The other great thing about Robocopy is that it is incremental - so any files that already exist in the target location will not be copied, unless they have been updated more recently on the source server. So if no one makes any changes to any files, nothing will be copied. Obviously this saves a lot on network bandwidth and processing.
So what you would do is set Robocopy to mirror your live server's files onto the spare server every 15 minutes or something like that (it depends how much data we are talking about, if its just a couple of GB then you could do it every 5 minutes really) and then if your live server goes down you have a copy of all the data that is, at most, 15 minutes old.

Hope that helps
Chris

[tendemo]

G Thanks Chris very interesting advice with an intuitive approach I'm sure I will get sorted out hence will mark this thread as solved when done. Cheers

[Lord Orwell]

building on to that, if you were to install an extra network card in each server so they communicated directly with each other, you wouldn't affect network bandwidth at all (requires crossover cable - total cost of two cards and cable about $40). Plus, this gives each server a way to monitor the other server to make sure it's still operating. You could write a simple program that enables the network access of the 2nd server if it detects the 1st server is no longer connected to the 2nd one.

[chris128]

That is a good idea actually, i've not heard of anyone doing that before. The only caveat is that both servers have to be fairly near each other I guess.

[Lord Orwell]

That is a good idea actually, i've not heard of anyone doing that before. The only caveat is that both servers have to be fairly near each other I guess.

how far apart are they?

[tendemo]

In my case Im think about a distance of 50 to 100 metres apart.
Cheers

[Lord Orwell]

In my case Im think about a distance of 50 to 100 metres apart.
Cheers

you can get cat-5 cable up to 300 feet, or nearly 100 metres. A repeater can extend the range. Let us know what you finally came up with to do.

Now, if your server is an actual "server" box, most of them contain redundant hardware anyway. The one i used to have had spare hard drives, dual power supplies, and two network ports. The only required hardware to function that there wasn't an automatic backup of was the motherboard, and it actually had two processors on it.