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Old 02-24-2016, 03:54 AM   #1
ravishchugh
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Smile Implementing real time hot standby


Hi all,

I have to create a system wherein the data is received in real time and an application is processing it. Now, I have to provide a Hot Standby for the main system which will takeover as soon as the main goes down and within fraction of seconds.

How do i go about it?

Regards
 
Old 02-24-2016, 04:31 AM   #2
tshikose
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Use a cluster.
 
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Old 02-26-2016, 02:06 AM   #3
ravishchugh
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Quote:
Originally Posted by tshikose View Post
Use a cluster.
Thanx Tshikose
 
Old 03-14-2016, 04:12 AM   #4
ravishchugh
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Originally Posted by tshikose View Post
Use a cluster.
But will cluster work for real time operations??
 
Old 03-14-2016, 01:43 PM   #5
rtmistler
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Firstly where the data is received in real time is therefore not Linux but instead a true real time embedded system either direct CPU or an Real Time Operating System (RTOS). OR ... Linux is capable of dealing with the data input rapidly enough such that it does not matter, and true time stamps are not necessary, just FIFO processing where time is agnostic.

Where an application is processing it, can be Linux.

Hot standby is a mirror which processes the same as the primary. And there needs to be signaling to indicate whether primary is operational or not, so that the secondary can become active. Signaling within a fraction of seconds implies once again, real time knowledge of events. Thus while the "application" might be Linux, I'd not trust something needing to be fault tolerant to any general OS.

This is not some trivial project. You can emulate, but if you wish to make a real commercial product and also scale this to something large such as a communications or file server, then you are generally talking custom embedded design. As far as a project, for school or personal experimentation, I'd then explore one of the various hobby kits of embedded micro-controllers and do something very rudimentary such as accelerometry measurements and process one set of signal inputs through two separate real-time boards, channeling those measurements to two different application PCs where you also specify a custom protocol to indicate that the primary has failed and thus the secondary needs to take over, and vice-versa.
 
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Old 03-16-2016, 07:01 AM   #6
bigearsbilly
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try this:

http://www.haproxy.org/
 
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Old 03-19-2016, 03:10 PM   #7
ravishchugh
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Thanx rtmistler and bigearsbilly....immensely helpful replies....i had a look over at linux-ha and corosync and found them to be quite useful.
But i got stuck on one thought though. My structure is as follows:-

I have 2 PCs running the same custom software and i can connect them using ethernet. The inputs to these PCs is coming via a fan out unit (serial port). Now the outputs of these will have to be pushed to a third PC via an ethernet port.

So to implement HA, as per my understanding, ill have to do following :-

Store the outputs of application in a database on main and standby machines. Use the 3rd PC as the client PC which is querying for outputs from these main and standby PCs via a floating IP address. It will fetch the data from the DB and display it.
I presume there will be an inherent time gap in this process.

Is this the right way or is there any other way out??

IS there a way to directly push the data to a Display device without the need of 3rd PC and still implement HA using only main and standby PCs?

Regards
 
Old 03-19-2016, 07:08 PM   #8
tshikose
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Hi,

Please tell us for which service do you really want to achieve HA?
 
Old 03-20-2016, 12:53 AM   #9
ravishchugh
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Hi,

Please tell us for which service do you really want to achieve HA?
Its a custom application which is being developed and gives the heading and lat long kind of data sir.
 
Old 03-24-2016, 07:27 AM   #10
bigearsbilly
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How far have you got?
 
  


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