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  1. #1

    What does "redundant" mean exactly?


    .... when a hosting company uses that word...? Does it mean that they have connections from 2 separate ISPs into their data centre? And if one fails, it'll automatically switch over to the other one, without a break in the service?
    How does this whole shebang work?


    Thanks.

  2. #2
    we don't know.
    since there's no copyright on the use of the word "redundant", only the hosting company in question can answer that ultimately.
    redundant what? staff? hardware? linux distributions? coffee mugs?

  3. #3
    Linux Guru
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    Usually it means there is an unused resource that is available in case of failure. I worked for a telco for a number of years and our critical resources were geographically isolated as well as having redundant failover. There would be two sets of everything at each location and two locations so a physical event wouldn't stop the all important business of making phone calls.

    I doubt that a hosting company would go that far.

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  5. #4
    Linux Engineer TNFrank's Avatar
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    re·dun·dant
    adjective \ri-ˈdən-dənt\

    : repeating something else and therefore unnecessary

    —used to describe part of a machine, system, etc., that has the same function as another part and that exists so that the entire machine, system, etc., will not fail if the main part fails
    No matter where ya' go, there ya' are.

  6. #5
    Quote Originally Posted by gregm View Post
    there is an unused resource
    Does this resource mean an internet connection?

  7. #6
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    Quote Originally Posted by resetreset View Post
    Does this resource mean an internet connection?
    Internet connection[s], hardware servers, software daemons, routers etc. Depends on the level of redundancy.

  8. #7
    So there are in fact, multiple ISPs into one centre, at least it could be? How do you put TWO ethernet cables into ONE server, and make sure that if one goes out, it starts using the other one seamlessly? I read somewhere that this wasn't possible....?

  9. #8
    Many servers have multiple Ethernet ports. Quad ports are not uncommon. If there is truly redundant ISP uplink this is usually done at the router and often with redundant routers and switches. It is a common feature of enterprise grade software and hardware to support failover to a backup ISP.

  10. #9
    Quote Originally Posted by Monkadelicd View Post
    Many servers have multiple Ethernet ports. Quad ports are not uncommon. If there is truly redundant ISP uplink this is usually done at the router and often with redundant routers and switches. It is a common feature of enterprise grade software and hardware to support failover to a backup ISP.
    Yeah, HOW?
    HOW is it done at the router? How do you know when your connection fails? Is there some computer just pinging away 24/7 to detect that?

  11. #10
    Most routers have a failover and load balancing function that is configured to failover to a backup WAN(internet) connection if the primary goes down.
    There are usually multiple ways of testing for connectivity. Ping can be used to test. There are protocols for failover to a backup link. Look up HSRP, VRRP.

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