Hi, I'm building new infrastructure with only two (2) servers (don't laugh, read on please) for my company. I've been talking to vendors but the information I get for High Availability (AlwaysOn) is not clear enough even some of them different even though they are Microsoft certified partners.
With the research on the internet, I found the new SQL Server 2012 has High Availability (AlwaysOn) feature that could act as SQL Failover, and then I request quote to vendors yet reply I receive from them doesn't match with what I've been reading on the internet even one of them doesn't know what is Active-Active/Active-Passive scheme.
Here's some understanding and question I found:
- Microsoft Windows Server doesn't care if it is acting as active or passive. I would need 2 Windows Server Standard license (cheaper) since the different between Standard and Data Center is only virtualization rights and I will be using High Availability (AlwaysOn) feature from SQL Server.
- High Availability (AlwaysOn)SQL Licensing confusion.
Licensing SQL Server for High Availability SQL Server software can be configured so that if one server fails, its processing will be picked up, recovered and continued by another server. All editions of SQL Server 2012 provide basic high availability features including backup log shipping, database mirroring and two-node failover clustering.Advanced (AlwaysOn) high availability features in SQL Server 2012 Enterprise Edition include enhanced support for multiple, active (readable) secondary servers and support for multi-site failover clustering. Log shipping and database mirroring take place at the database level, whereas failover clustering takes place at the SQL Server instance level.
AlwaysOn Availability Groups New for the SQL Server 2012 Enterprise Edition,AlwaysOn Availability Groups enable customers to configure multiple databases that will failover as a unit, with support for up to four active secondary servers and two synchronous secondary servers. The ability to use secondary servers for more than just passive failover support can improve the performance of primary, reporting and backup workloads due to better balancing of workloads across instances, helping to provide better return on hardware investment. Note: When secondary servers are actively used to support these additional workload scenarios—that is, when the servers used for failover purposes are no longer truly passive—they must be fully licensed accordingly.
Most vendors stating that High Availability (AlwaysOn) is Active/Active scheme. But from SQL Server 2012 Licensing Reference Guide, I could use the first server for my active node and the second one for my passive node, so in case my first server breaks the second one will take over.
Which one is correct, is High Availability (AlwaysOn) is Active/Active or Active/Passive scheme? Or is there any certain scenario that could change the scheme vice versa?
In this link, quote,
"With SQL Server 2012 AlwaysOn your solution does not have to utilize shared storage, but can use SAN, DAS, NAS or Local Disk depending on your budget and requirements."
Which I come to conclusion that I don't need shared storage when I configuring the servers, but in thislink,quote,
"AlwaysOn Availability Groups does not depend on any form of shared storage. However, if you use a SQL Server failover cluster instance (FCI) to host one or more availability replicas, each of those FCIs will require shared storage as per
standard SQL Server failover cluster instance installation."
And the answer I receive from certain vendor,
"If you use Always On Availability Groups, you can now deploy different instances (non-failover instance) of SQL Server in a Window Server Failover Cluster, each can have its own local disk. Otherwise, Shared storage is required."
In my understanding, High Availability (AlwaysOn) is use to replicate databases from one node to another, in my case the first node (active) to the second node (passive) and High Availability (AlwaysOn) is a automated failover. Is it really automated failover or it just do replication to another node or it must be set on application we used detecting if the first server down and we have to connect to the second one?
Do I really need shared storage to use High Availability (AlwaysOn), I don't like the idea using shared storage because of single point of failure and to add another shared storage is expensive for now?
How High Availability (AlwaysOn) differs from SQL Server failover cluster instance?
I hope someone shed a light for me and pull me out of this confusion.
Thanks for reading.