May 11, 2016 at 9:20 pm
Hi ,
We currently have a SQL Server Failover Cluster and they want implement Always On availability group. But getting rid of the SQL Server Failover Cluster. I'm aware that this 2 technologies have different level of protections, my suggestion will be the combination of this two features, but what is your opinion?
Thanks
May 11, 2016 at 9:45 pm
APA0876 (5/11/2016)
Hi ,We currently have a SQL Server Failover Cluster and they want implement Always On availability group. But getting rid of the SQL Server Failover Cluster. I'm aware that this 2 technologies have different level of protections, my suggestion will be the combination of this two features, but what is your opinion?
Thanks
Opinion shouldn't be involved when it comes to a company's infrastructure High Availability and Disaster Recovery constructs and plans. They need to be well thought out and reasoned, carefully implemented and maintained and tested. Sorry to be blunt, but you have given us precisely zero information on which to guide you. I will add that every company out there should base their HA/DR plan on guidance from qualified professionals (internal or otherwise), not from some forum posts.
To directly answer your question though the combination of AG/FCI is very complex with lots of nuances and caveats and provisos. I advise clients against that pair in most situations.
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
May 12, 2016 at 3:08 am
The shortest possible answer to your question is, yes, Availability Groups can substitute for Failover Clusters. However, as Kevin says, we really don't know enough about your situation to make a good recommendation.
The strengths inherent in the AG is that it is shared nothing. You don't have to have a single point of failure, a shared disk. Instead, each of the systems can be completely independent. However, I've seen people set that up, but with a common shared SAN. In short, they gained nothing.
Making this decision really does depend on the details of your situation.
----------------------------------------------------The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood... Theodore RooseveltThe Scary DBAAuthor of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd EditionProduct Evangelist for Red Gate Software
May 12, 2016 at 8:37 am
Hi,
Thanks for your comments, I posted the comment to get some feedback from this community, as I value this forum, I will continue the post:
We are aware that these are two different kind of technologies, with different protection levels, FCI: Server Instance level protection, and AAG : Database Level protection ,
We know that the FCI has a SPOF the SAN, we are just evaluating the possibility of having the Combination of both technologies to take advantage of both protection levels.
May 12, 2016 at 12:41 pm
All of your answers you seek are available from Microsoft...
Taken from https://msdn.microsoft.com/en-us/library/ff877884.aspx
An availability group supports a failover environment for a discrete set of user databases, known as availability databases, that fail over together
Deploying AlwaysOn Availability Groups requires a Windows Server Failover Clustering (WSFC) cluster
In short you cant have one without the other...
May 12, 2016 at 12:49 pm
Smendle (5/12/2016)
All of your answers you seek are available from Microsoft...Taken from https://msdn.microsoft.com/en-us/library/ff877884.aspx
An availability group supports a failover environment for a discrete set of user databases, known as availability databases, that fail over together
Deploying AlwaysOn Availability Groups requires a Windows Server Failover Clustering (WSFC) cluster
In short you cant have one without the other...
The OP wasn't confused or asking about WSFC. He was asking about a SQL Server Failover Cluster Instance.
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
May 12, 2016 at 12:52 pm
TheSQLGuru (5/12/2016)
Smendle (5/12/2016)
All of your answers you seek are available from Microsoft...The OP wasn't confused or asking about WSFC. He was asking about a SQL Server Failover Cluster Instance.
My apologies I see Failover Cluster and think Windows.......
I guess the real question is do you want granularity on your Database server failover or do you just want the whole server to failover?
If you want granularity then use AG, if you want the whole server to failover then SQL Failover works fine....
May 12, 2016 at 1:18 pm
Smendle (5/12/2016)
TheSQLGuru (5/12/2016)
Smendle (5/12/2016)
All of your answers you seek are available from Microsoft...The OP wasn't confused or asking about WSFC. He was asking about a SQL Server Failover Cluster Instance.
My apologies I see Failover Cluster and think Windows.......
I guess the real question is do you want granularity on your Database server failover or do you just want the whole server to failover?
If you want granularity then use AG, if you want the whole server to failover then SQL Failover works fine....
Hi, Thanks, Ideally having both options would be the best scenario as we will have 2 layers of protection, we have a discussion about it, as the Always On is new to us, I want to make sure that the whole team be clear of what we miss if we get rid of the SQL Server FCI, (which means instance Level protection) and AAG means just Database Level protection, based on that I keep thinking that AAG cannot substitute FCI,
May 12, 2016 at 1:41 pm
...Always On is new to us...
PLEASE remember my initial statement about "qualified professional"!!! The company's very survivability is on the line here. And yes, I have seen companies go out of business or be sold for pennies on the dollar because they didn't know what they were doing along these lines!
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
May 12, 2016 at 1:48 pm
TheSQLGuru (5/12/2016)
...Always On is new to us...
PLEASE remember my initial statement about "qualified professional"!!! The company's very survivability is on the line here. And yes, I have seen companies go out of business or be sold for pennies on the dollar because they didn't know what they were doing along these lines!
Hi Kevin,
The fact that the Technology is new to us , does not mean that we are not fully qualified to acquire it/ implement it and maintain it/ by our self, either way thanks for taking your time to write your comment "very helpful!!!"
May 12, 2016 at 1:53 pm
APA0876 (5/12/2016)
Smendle (5/12/2016)
TheSQLGuru (5/12/2016)
Smendle (5/12/2016)
All of your answers you seek are available from Microsoft...The OP wasn't confused or asking about WSFC. He was asking about a SQL Server Failover Cluster Instance.
My apologies I see Failover Cluster and think Windows.......
I guess the real question is do you want granularity on your Database server failover or do you just want the whole server to failover?
If you want granularity then use AG, if you want the whole server to failover then SQL Failover works fine....
Hi, Thanks, Ideally having both options would be the best scenario as we will have 2 layers of protection, we have a discussion about it, as the Always On is new to us, I want to make sure that the whole team be clear of what we miss if we get rid of the SQL Server FCI, (which means instance Level protection) and AAG means just Database Level protection, based on that I keep thinking that AAG cannot substitute FCI,
The granularity at the database level would be "better" protection when you have a scenario where your databases are stored on multiple drive arrays (separate from each other) and should one array fail you are only failing over that database on the failed HW instead of failing over the entire instance because of 1 failed array....
I don't believe you would want AG AND SQL Failover at the same time unless the rules for failover were such that each failover event was mutually exclusive of the other, in which case you would be effectively isolating out the SQL failover rules in favor of the more granular AG rules.
May 12, 2016 at 2:07 pm
APA0876 (5/12/2016)
TheSQLGuru (5/12/2016)
...Always On is new to us...
PLEASE remember my initial statement about "qualified professional"!!! The company's very survivability is on the line here. And yes, I have seen companies go out of business or be sold for pennies on the dollar because they didn't know what they were doing along these lines!
Hi Kevin,
The fact that the Technology is new to us , does not mean that we are not fully qualified to acquire it/ implement it and maintain it/ by our self, either way thanks for taking your time to write your comment "very helpful!!!"
I have come across MANY over the years who felt the same way and then got their eyes opened (almost always AFTER the fact) by all of the caveats, limitations, provisos, gotchas, etc that are part-and-parcel of Always On.
I wish you the best in your planning and migration efforts!
Best,
Kevin G. Boles
SQL Server Consultant
SQL MVP 2007-2012
TheSQLGuru on googles mail service
May 12, 2016 at 3:26 pm
Smendle (5/12/2016)
TheSQLGuru (5/12/2016)
Smendle (5/12/2016)
All of your answers you seek are available from Microsoft...The OP wasn't confused or asking about WSFC. He was asking about a SQL Server Failover Cluster Instance.
My apologies I see Failover Cluster and think Windows.......
I guess the real question is do you want granularity on your Database server failover or do you just want the whole server to failover?
If you want granularity then use AG, if you want the whole server to failover then SQL Failover works fine....
It's more than just granularity on failover though. Remember, a failover cluster instance must have a shared drive. Must. No options. While an Availability Group can have completely separate systems, not even in the same building or on the same continent (async is your friend). The differences between the two is not simply database versus server. There's a lot to it.
----------------------------------------------------The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood... Theodore RooseveltThe Scary DBAAuthor of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd EditionProduct Evangelist for Red Gate Software
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