October 30, 2017 at 2:08 am
Hello All,
As per my understanding SQL Server clustering is one of the best methods to provide HA. Having two nodes with SQL Server instance installed on both with a common SAN/NAS storage having system and user databases. If one node goes down other one gets active pointing to the shared SAN. So far so good. However what if SAN gets failed. How do we plan for it ? In case u say about SAN replication then how will the cluster with both nodes behave in case of SAN failure. I am little lost here.
October 30, 2017 at 8:09 am
As always: it depends !
With a SQLServer clustered instance, the pain point may be the shared storage.
A single SAN is such a liability ( and still have a risk of going down ), so, SAN replication may get you a solution for that if you have 2 SANs on more than one location.
There can also be issues with the switches, SAN-cards, ...
In such case failover with regards to LUN(s) can be setup as "transparant" for your SQLinstance or as "still needs manual intervention".
I haven't had the occasion to pull the plug one of our sans to see if it actually works as designed !
Use the search engine of your preference and search for "SAN Storage Best Practices for SQL Server". Many vendors have published their vision for their product(s) for such solution.
Have you taken a look at SQLServer Always On Availability Groups ( launched with SQL 2012 ) ? Check https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/overview-of-always-on-availability-groups-sql-server
This provides a non-shared-storage solution with failover capability. ( but still needs a Windows cluster for SQL 2014 AGs )
Johan
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October 30, 2017 at 12:29 pm
ALZDBA - Monday, October 30, 2017 8:09 AMA single SAN is such a liability ( and still have a risk of going down ), so, SAN replication may get you a solution for that if you have 2 SANs on more than one location.
There can also be issues with the switches, SAN-cards, ...
In such case failover with regards to LUN(s) can be setup as "transparant" for your SQLinstance or as "still needs manual intervention".
I haven't had the occasion to pull the plug one of our sans to see if it actually works as designed !
I don't know the deep details (I trust our OPS folks and they re-earn that trust on a regular basis) but we use "SAN-Over-The-WAN" replication to our remote DR site and we do a yearly full blown DR/BCP (Business Continuity Plan) test every year. It takes less than an hour to be full up and running.
--Jeff Moden
Change is inevitable... Change for the better is not.
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