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Multiple SQL clustering options

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  • Multiple SQL clustering options


    Im investigating providing redundancy for our SQL servers in our production environment, which currently consists of 4 standalone SQL servers. Im trying to find an economic way to provide redundancy for these servers and from my research I understand that I have a few options in form of to clustering.

    Option 1: Add all four servers into a single cluster as active nodes and add a fifth as a passive node to provide redundancy if one fails. However clustering >2 nodes require purchasing SQL enterprise edition which is four times the cost of standard which makes this option very expensive.

    Option 2: Add each server into a separate 2 node active/passive cluster with new physical servers. So wed have 8 physical servers with 4 active and 4 passive in a one to one match. Since wed be using 2 node clusters we can use SQL standard and purchasing four new physical servers is cheaper then licensing cost of SQL enterprise.

    Option 3?: Is it possible for me to add a fifth physical server and have it be a member multiple clusters? In this case have each of the four SQL servers enter a 2 node active/passive cluster with the fifth. I doubt this is possible but it would be more economical.

    Alternatively is there other options Im not aware of in terms of clustering setup or an alternative to clustering to provide automatic reliable SQL redundancy? Im looking into database mirroring but it seems to be similar to option 2. Ideally I'd like to avoid having to install Active Directory at our production environment but I think it will be necessary.

    Thanks for any insight.

  • #2
    Re: Multiple SQL clustering options

    Firstly, it would help to know which version of SQL Server you're using. 2000? 2005? 2008? 4.2??

    While you're looking at mirroring/clustering the actually server, you may have overlooked the possibility of database level mirroring and redundancy. For example, you could use SQL Server database mirroring to replicate individual databases to other instances. Using the "Synchronous with automatic failover" method may be robust enough for you. You will need "witness" servers / instances but you can use the free Express Edition of SQL Server to act as the witness.

    It may be possible to implement this without purchasing extra hardware and only buy new licenses. Install a new instance of SQL Server on each server and then mirror the individual databases that reside on a different server. A better solution might be to purchase a single failover server, install SQL Server on it, and then use "Synchronous with automatic failover" mirroring on it to mirror all of the other databases on each of the four servers. Of course, this depends on how heavy the databases are used. High availability mirroring methods take up extra processing power and network resources. Research database mirroring and see if it fits your needs.
    Wesley David
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    • #3
      Re: Multiple SQL clustering options

      Thanks for the tip and I'll take a look into Synchronous with automatic failover.

      Not sure how I forgot to mention that we're using Windows 2003 with SQL 2000, however we will be migrating to SQL 2005 in the next few months, possibly at the same time we implement redundancy. We're waiting for 2008 to have more time on the market.