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  1. #1
    Join Date
    Aug 2004

    what is "High-Availability"

    what is "h-a" as related to a linux cluster...

    does it pertain only to clusters. what about multi-CPU system

  2. #2
    Senior Member
    Join Date
    Jul 2004
    it usually refers to fault tolerance of some sort. if one system/server/drive/whatever kicks the bucket, another system/server/drive/whatever kicks in and take it's place without any service downtime.
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  3. #3
    Senior Member
    Join Date
    Dec 2003
    Pacific Northwest

    The below information is provided:

    High Availability

    As more and more critical commercial applications move on the Internet, providing highly available services becomes increasingly important. One of the advantages of a clustered system is that it has hardware and software redundancy. High availability can be provided by detecting node or daemon failures and reconfiguring the system appropriately so that the workload can be taken over by the remaining nodes in the cluster.

    Example implementations of HA

    In this example we will theoretically create an Active/Passive cluster running an apache server, serving the intranet.

    To create this small cluster, we will use one good machine with lots of RAM, and many CPUs and another one with just enough RAM/CPU to run the service. The first machine will be the master node while the second will be backup node. The job of the backup node is to take over the services from the master node if it thinks that the master node is not responding.

    Cruise on over to http://www.google.com/linux then enter “High Availability” in the Search Box and press Google Search. You will find a multitude of results relative to your inquiry.

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  4. #4
    Senior Member gore's Avatar
    Join Date
    Oct 2002
    High availability, like your GF, won't go down on you much.


  5. #5
    Blast From the Past
    Join Date
    Jan 2003
    HAHAHAHAHAHAHAHAHA omg gore your horriable
    id give you greenies but i still cant since the last time i did
    work it harder, make it better, do it faster, makes us stronger

  6. #6
    Senior Member
    Join Date
    May 2003
    HA features are meant to be implemented for Mission Critical Activities... In simple terms it implies implementing redundancy into your servers in means of its Power Supply, Memory, Hard Disk, Even CPU. The aim is very simple To eliminate Single Point of Failure for mission critical activities

    The High availability solution can be implemented using technologies like clustering , mirroring, SAN replication, Hot swap features for many hardware devices, Pre-Failure alarms for early detection of problems, making OS failover proof etc.

    I hope this will give you some idea on the concept...
    ****** Any man who knows all the answers most likely misunderstood the questions *****

  7. #7
    Just Another Geek
    Join Date
    Jul 2002
    Rotterdam, Netherlands
    HA is the difference between 99% and 99.999% uptime (the last one meaning only 5 min. downtime a year!). It's all about how much "nines" you can handle

    To get HA one usually resorts to clustering or hot-standby as it's the 'easiest' way to get 99.999% uptime (of your application).

    A cluster has the added bonus of being able to load-balance. A hot-standby doesn't do anything (accept to keep state) until the "main" server/networkequipment dies. So it usually just sits there gathering dust.
    Oliver's Law:
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  8. #8
    Senior Member
    Join Date
    Nov 2001
    Originally posted here by SirDice
    A cluster has the added bonus of being able to load-balance. A hot-standby doesn't do anything (accept to keep state) until the "main" server/networkequipment dies. So it usually just sits there gathering dust.
    Actually, there are "clusters" that do not load balance, that is a specific type of clustering. "Hot-standby" is considered a form of clustering (called Failover clustering by some). There are other cluster types as well.
    Wikipedia has some good info for those interested. Follow the link to the "Two Node Cluster" reference.
    Chris Shepherd
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  9. #9
    Senior Member
    Join Date
    Jul 2003
    Originally posted here by gore
    High availability, like your GF, won't go down on you much.
    But if you have a girlfriend cluster then maybe... one goes down, the other maintains the HA?

    Or in the case of a demanding environment, one goes down, the other too [maintaining HA] thus ensuring a competitive service.

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