Level 1: What is "SQL Server AlwaysOn"?

  • Perry Whittle

    SSC Guru

    Points: 233678

    Comments posted to this topic are about the item Level 1: What is "SQL Server AlwaysOn"?

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    [font="Tahoma"]"Ya can't make an omelette without breaking just a few eggs"[/font] 😉

  • Ian Massi

    SSCertifiable

    Points: 5931

    The timing of this stairway is excellent. I'm looking at setting up AlwaysOn in my environment and this first article is excellent to explain the different components to my manager and the server/network guys.

  • Perry Whittle

    SSC Guru

    Points: 233678

    Hi

    Thanks for the comments please don't forget to rate the article if you found it useful

    Regards Perry

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    [font="Tahoma"]"Ya can't make an omelette without breaking just a few eggs"[/font] 😉

  • Jerry Hung

    SSChampion

    Points: 12858

    Thanks for this timely introductory article, as I am doing research on AlwaysOn this week 🙂

    Some requirements though

    AG Group is only available on Enterprise edition @@ = costly. I believe Replicas can be on Standard edition?

    AG has to be on a Cluster node = again, costly vs. Log Shipping/Mirroring (deprecated) where one can do it on standalone to standalone

    Features Supported by the Editions of SQL Server 2014

    http://msdn.microsoft.com/en-us/library/cc645993.aspx#High_availability

    SQLServerNewbie MCITP: Database Administrator SQL Server 2005
  • Perry Whittle

    SSC Guru

    Points: 233678

    Jerry Hung (9/24/2014)


    Thanks for this timely introductory article, as I am doing research on AlwaysOn this week 🙂

    Thank you, it's a 9 level stairway, there are 8 more levels to come yet 😉

    Please rate the article if you found it useful

    Jerry Hung (9/24/2014)


    AG Group is only available on Enterprise edition @@ = costly.

    Hey, there's no such thing as a free lunch 😉

    Jerry Hung (9/24/2014)


    I believe Replicas can be on Standard edition?

    No, this link details the following

    SQL Server AlwaysOn Pre Reqs and Restrictions


    Each server instance must be running the Enterprise Edition of SQL Server 2012\2014

    Jerry Hung (9/24/2014)


    AG has to be on a Cluster node = again, costly vs. Log Shipping/Mirroring (deprecated) where one can do it on standalone to standalone

    Yes a cluster node is required but where do you get that the cost is higher? Windows 2012 Standard supports clustering and if you're not using shared storage to support an FCI as a replica then cost shouldn't be an issue. All of your servers will likely have at least Windows 2012 Standard edition. Also don't forget that to get full mirroring features this required Enterprise edition of SQL server 😉

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    [font="Tahoma"]"Ya can't make an omelette without breaking just a few eggs"[/font] 😉

  • Jerry Hung

    SSChampion

    Points: 12858

    Perry Whittle (9/24/2014)


    Jerry Hung (9/24/2014)


    Thanks for this timely introductory article, as I am doing research on AlwaysOn this week 🙂

    Thank you, please rate the article if you found it useful

    Rated Excellent!

    Jerry Hung (9/24/2014)


    I believe Replicas can be on Standard edition?

    No, this link details the following

    SQL Server AlwaysOn Pre Reqs and Restrictions


    Each server instance must be running the Enterprise Edition of SQL Server 2012\2014

    Well that sucks

    Perry Whittle (9/24/2014)


    Jerry Hung (9/24/2014)


    Jerry Hung (9/24/2014)


    AG has to be on a Cluster node = again, costly vs. Log Shipping/Mirroring (deprecated) where one can do it on standalone to standalone

    Yes a cluster node is required but where do you get that the cost is higher? Windows 2012 Standard supports clustering and if you're not using shared storage to support an FCI as a replica then cost shouldn't be an issue. All of your servers will likely have at least Windows 2012 Standard edition. Also don't forget that to get full mirroring features this required Enterprise edition of SQL server 😉

    Sadly, no Windows 2012 for OS at work yet @@ so I am testing SQL 2014 on Windows 2008 R2 (which is probably not ideal AG setup anyway)

    I meant "higher cost" as in Clustering usually needs 2 nodes vs. 1 (unless we set up a 1-node Cluster, ha, I know the Pros on this)

    If I understand correctly,

    AG Primary (2-node cluster) -> AG Replica (2-node cluster) = 4 nodes minimum usually, SQL Enterprise = $$$$$

    SQLServerNewbie MCITP: Database Administrator SQL Server 2005
  • Perry Whittle

    SSC Guru

    Points: 233678

    Jerry Hung (9/24/2014)


    Rated Excellent!

    keep an eye out for the remaining 8 levels of the stairway 😉

    Jerry Hung (9/24/2014)


    Sadly, no Windows 2012 for OS at work yet @@ so I am testing SQL 2014 on Windows 2008 R2.

    Hmm, check out the price of Windows 2008 R2 Enterprise edition as Windows 2012 Standard has re aligned.

    Jerry Hung (9/24/2014)


    I meant "higher cost" as in Clustering usually needs 2 nodes vs. 1 (unless we set up a 1-node Cluster, ha, I know the Pros on this)

    True, clustering needs at least 2 nodes to fully function, but then, an AlwaysOn group requires as many nodes as you'll have replicas.

    If you plan an AlwaysOn group with 4 replicas you'll need 4 nodes. An AlwaysOn replica must reside on a separate node to all other replicas in the group, this is a pre req which is checked when enabling the AlwaysOn group configuration.

    Jerry Hung (9/24/2014)


    If I understand correctly,

    AG Primary (2-node cluster) -> AG Replica (2-node cluster) = 4 nodes minimum usually, SQL Enterprise = $$$$$

    What you're describing here is an AlwaysOn group configuration where both replicas are FCIs, the restrictions doing this are huge and also re introduce the storage single point of failure since you'll need shared storage for each of the FCIs.

    AlwaysOn groups ideally use standalone instances of SQL server, it's just that all the nodes are joined to the same Windows cluster.

    Just because your nodes are in a Windows cluster doesn't mean you automatically have to deploy FCIs, in fact don't, otherwise you cannot utilise automatic failover in the AlwaysOn group 😉

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    [font="Tahoma"]"Ya can't make an omelette without breaking just a few eggs"[/font] 😉

  • Miles Neale

    SSChampion

    Points: 13147

    Thanks excellent information and very readable.

    (Already rated)

    Not all gray hairs are Dinosaurs!

  • quackhandle1975

    SSChampion

    Points: 10963

    Nice article, looking forward to the next in the stairway.

    qh

    [font="Tahoma"]Who looks outside, dreams; who looks inside, awakes. – Carl Jung.[/font]
  • Perry Whittle

    SSC Guru

    Points: 233678

    quackhandle1975 (10/27/2014)


    Nice article, looking forward to the next in the stairway.

    qh

    Here you go

    http://www.sqlservercentral.com/articles/AlwaysOn/107537/[/url]

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    [font="Tahoma"]"Ya can't make an omelette without breaking just a few eggs"[/font] 😉

  • akljfhnlaflkj

    SSC Guru

    Points: 76202

    Thanks for the article.

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