By Craig P

2019-01-07 14:59:12 8 Comments

I have two servers in always on failover configuration with windows clustering underneath.

Do both servers need to have the same memory?
One of our DBs that uses a lot of memory is not in the AG, so ideally I don't want to give the secondary server the same memory as the primary because - it will never need to run the big DB.


@rvsc48 2019-01-07 15:06:55

Thinking about the future, databases will come and go most likely. Do you want that extra pain of remembering that one of the servers in the AG configuration is not set the same? We always set the memory the same in all servers involved.

Also, if you have to run all databases on one server (the one with lesser memory) for any extended time, you do not have to adjust the "max server memory" instance level setting because of a lower amount of available physical memory.

@sajeesh 2019-01-07 19:50:16

They need not have same amount of memory, there is is no pre-requisite as such. However it would be good to allocate sufficient memory that would take care to run databases if AG was to fail-over and databases were to be online on the other server instance. I would suggest that you calculate the Memory requirement separately for databases part of Always ON and standalone ones and accordingly provision it accordingly across servers/instances.

@Josh Darnell 2019-01-07 15:12:36

There's no functional requirement for servers in a cluster to have the exact same specs (memory, CPU, etc). So you can definitely set it up this way.

To some extent, you've answered your own question. To put it differently - if one of the servers in the cluster will never be running the same workload as the other, you should tune that server appropriately for its workload. It would be a waste of resources to do otherwise.

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