October 30, 2007 at 10:40 am
This is something that I have never actually had to answer before and really haven't thought about before because it hasn't come up till now...
I have a 3 node cluster, 2 active nodes that fail over to the 3rd node. Each active node has a single instance of SQL Server running on it. Both active nodes are currently set to use 3.5 GB of memory for SQL Server. So, if the worst case scenario happens and both active nodes must fail-over to the 3rd node making both sql instances active on a single machine, do I need to make sure that the 3rd node will have enough ram to handle both instances or will Windows use virtual memory to handle this worst case scenario???
The reason this has never come up to me before is because I always had redundant setups in the past with a fail-over for each active server so I am at a loss on this one. The reason I am asking is that one of the instance would be helped out by increasing the amount of RAM made available to it (using AWE32 etc...) but I am concerned about the possibility of both instance failing over to that passive node (should not happen but I like to mitigate things when possible)...
So, right now, each server has 8 GB of RAM and I would actually like to alter the settings for both active nodes to use it all instead of the 4 GB they are making use of right now (approx).
Comments? Suggestions?
October 30, 2007 at 11:52 am
As long as the prodcution nodes are configured to use a static amount of memory you should be ok. But, the 3rd node needs to be sized to handle both.
If nodes 1 & 2 were set to dynamically configure memory, this would be an issue on failover.
Node 1: 3.5 Gig
Node 2: 3.5 Gig
Node 3: 8 Gig
If you want to use 8 Gig on Node 1 and Node 2, then you need 16 gig on Node 3.
(this has always been a favored interview question on configuring Cluster's with SQL Server)
October 30, 2007 at 12:16 pm
Thanks. That is what I thought but I wanted to be sure before I went to ask my boss for more memory. 😉
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