December 3, 2008 at 10:03 pm
How many instances are recommended for SQL 2005 cluster environment (3 nodes - active/active/passive)? 50 instances is the max, but we should not go that far, I believe. Just like we will not have 1000 indexes for a table even it is allowed in theory.
Does any one have real world experience/story to share? Considering performance, resources usage, best practice, etc.
December 4, 2008 at 12:43 am
Hello Vivien,
Ideal recomendation for cluster is 1 instance on one box i.e. in your environment two instance which will be active / active / passive. Which itself is good combination as there won't be much load on there server as both the node will rarely run on the same system.
First of all need to find out why you need more instance? Can't you put it all DBs on the same instance? As each instance running will have seperate services running on server hence taking more resources.
But got very good article about this:
http://www.eggheadcafe.com/software/aspnet/29541042/how-many-instances-in-one.aspx
Hope this will help.
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"Thare are only 10 types of people in the world:
Those who understand binary, and those who don't."
December 4, 2008 at 3:16 am
clusters are either active\passive or active\active regardless of the number of nodes.
do you really need 50 instances? Remember that when a node fails the resources will be resumed on another node this could potentially cause performance problems. How many databases do you have? How many instances do you actually need?
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"Ya can't make an omelette without breaking just a few eggs" 😉
December 4, 2008 at 11:11 am
No need to reach the limit (50 instances). But there are cases have 16 instances on 4 nodes. "I've had 16 instances on serveral 4 node x64 clusters which is a fairly reasonable practical limit". Thanks free_mascot giving the link.
I saw an article/discussion about multiple instances on a cluster saying the performance related concerns. When the 2nd + instances loaded, SQL binary blah, blah… unfortunately, I lost that link, otherwise I can refer to. But I do want to know how the other people set those up and any lesson learned.
December 5, 2008 at 12:58 pm
Are drive letters a factor here at all? In the past, I've been limited to 3 instances on each node (of a 2-cluster node). If you have a drive for the data files, log files, backups and temp (that's 4 drives per) 3 instances = 12 drives. Assume you have a fail-over and the 3 instances on the other node all have to reside on one node for a while, that's 24 drives. In some cases, i did w/o the extra drive for tempdb if the system didn't use much of tempdb anyway.
I think I read in SQL 2008 you can now used named drives. Haven't looked at this yet though.
Tim White
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