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dewacorp.alliances
452 Posts |
 Posted - 2008-01-29 : 19:16:22
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| Hi allAt the moment, we've setup 2 nodes on our each SQL farm. Just want to clarify about the Active/Passive cluster mode, if we join another node into the cluster, technically it's still only 1 box is active and the other 2 are standby ... correct?I heard that some people has 4 or more in cluster ... I don't quite understand why it needs so many servers for standby. Unless I am missing the point by doing Active/Active which I thought this is not recommended on SQL/Exchange cluster environment?Any feedback regarding this that will be good.Thanks |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2008-01-29 : 23:13:57
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| If only have one instance in the cluster, you are correct. If cluster has more than two nodes, usually there are multiple sql instances. |
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dewacorp.alliances
452 Posts |
Posted - 2008-01-30 : 01:01:04
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quote:
Originally posted by rmiaoIf cluster has more than two nodes, usually there are multiple sql instances.
Can you explain it a bit further on this? |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2008-01-31 : 23:51:49
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| Usually you don't want four nodes to host one sql instance (one active node with three passive nodes), more likely you'll put three instances in the cluster (three active nodes with one passive node). |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2008-02-01 : 13:03:40
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| We've got 4 active nodes running 11 SQL instances. We spread the 11 instances across the 4 nodes according to their utilization. And it is not true that it isn't recommended.Tara KizerMicrosoft MVP for Windows Server System - SQL Serverhttp://weblogs.sqlteam.com/tarad/ |
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dewacorp.alliances
452 Posts |
Posted - 2008-02-05 : 15:50:34
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quote:
We've got 4 active nodes running 11 SQL instances. We spread the 11 instances across the 4 nodes according to their utilization.
Hi TaraI am very interesting with this model. We never setup the Active/Active cluster before.Couple questions though:1) Obviously, there are different between Active/Passive vs Active/Active significantly. If we have Active/Passive, can we turn this to Active/Active cluster?2) Correct if I am wrong here, you mentioned you have 11 instances spread among 4 servers. That means that for each instance you spread into 2 servers ... correct? Also, why do you need so many instances? Also, if you have 4 servers with each instance spread to 2 nodes, the maximum that you can get is 6 instances max. Am I missing soemthing here?3) I guess when you set this initially, you didn't know the load for each instance. How do you manage to choose which instance suit with server cause the box is shared among other instance. Or you might start with 2 servers first with 1 instance and then you add a new box and then you have another instance and so on.4) How's the spec for each btw (memory, cpu etc)?5) Do you know any documents/reference that can help us to do this?Thanks |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2008-02-05 : 16:49:24
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| 1. There is no difference between the two except that now you have instances running on both/all nodes. Nothing changes in the setup.2. An instance can only reside on one node, so your statement about spreading it onto 2 servers is incorrect. We use 11 instances for specific reasons that I'm not going to go into here. We split up the instances across the nodes according to their utilization. One node might have 1-2 instances, while another might have 4-5. It just depends on the load of the instance and which node isn't highly utilized. Your statement about 6 instances max is incorrect. 3. We did know the load of each instance, which is why we purchased 4 nodes. We didn't start with 2 as you have suggested. We immediately started with 4 to handle all of our SQL Server 2005 instances in that particular environment.4. Our nodes have 32GB of memory and 4 dual-core CPUs (operating system sees 8). This 4-node cluster is actually not as powerful as some of our other clusters. We are now purchasing quad-core servers (operating system sees n*4). 5. I don't have any documentation to provide to you. If you don't have the experience with such a setup, I'd highly recommend hiring a consultant to help you. Clustering is not something that you can easily learn.You seem to be under the impression that clustering provides load balancing of an instance. Clustering is for high availability and does not provide load balancing except if you have multiple databases that can be spread across multiple instances. But this is not true load balancing.Tara KizerMicrosoft MVP for Windows Server System - SQL Serverhttp://weblogs.sqlteam.com/tarad/ |
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dewacorp.alliances
452 Posts |
Posted - 2008-02-05 : 21:42:58
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quote:
An instance can only reside on one node, so your statement about spreading it onto 2 servers is incorrect. We use 11 instances for specific reasons that I'm not going to go into here. We split up the instances across the nodes according to their utilization. One node might have 1-2 instances, while another might have 4-5. It just depends on the load of the instance and which node isn't highly utilized. Your statement about 6 instances max is incorrect.
>>> I am taking the analogy of Passive/Active that we have (2 nodes). So we installed the Default instance on first node and this installation is available to the seconds nodes (that is for redunancy). Now if we taking into your 4 nodes. So you have 1st instance which will be available Node 1 and 2, 2nd instance you install on Node 1 and 3. 3rd instance you will install on Node 1 and 3. 4th instance on Node 2 and 3 and 5th instance on Node 2 and 4 and the last one 6th instance on Node 3. Unless you install another instance on instance on the same schenario above which I guess I'm not quite understand yet :) quote:
You seem to be under the impression that clustering provides load balancing of an instance. Clustering is for high availability and does not provide load balancing except if you have multiple databases that can be spread across multiple instances. But this is not true load balancing.
No ... I do understand the clustering is not load balancing. I just don't get it this model. Need more research on this.Thanks |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2008-02-05 : 21:51:36
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| No. All SQL instances are available to all nodes. When you run the install on node1, it also installs it on node2, node3, and node4 at the same time.So if I have instance1-10, I can put them anywhere amongst those 4 nodes. I could have instance1-3 on node1, instance4 on node2, instance5-9 on node3, and instance10 on node4. I could do any combination of those 10 instances amongst those 4 nodes. A node is passive as long as there are no resources running on it. So once you move a SQL instance to a node, it is now active.Tara KizerMicrosoft MVP for Windows Server System - SQL Serverhttp://weblogs.sqlteam.com/tarad/ |
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dewacorp.alliances
452 Posts |
Posted - 2008-02-12 : 04:18:50
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quote:
Originally posted by tkizer
No. All SQL instances are available to all nodes. When you run the install on node1, it also installs it on node2, node3, and node4 at the same time. So if I have instance1-10, I can put them anywhere amongst those 4 nodes. I could have instance1-3 on node1, instance4 on node2, instance5-9 on node3, and instance10 on node4. I could do any combination of those 10 instances amongst those 4 nodes. A node is passive as long as there are no resources running on it. So once you move a SQL instance to a node, it is now active.
You mentioned that "I could have instance 1-3 on Node1, instance4 on node2 etc". If you loose one of the box, let say Node1, basically you loose instance 1 - 3 ?!?! Where is the redundancy then? Thank you |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2008-02-12 : 13:22:06
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| No. You don't lose any instances if you lose a node. They move to one of the other nodes. You decide how to split up the instances amongst the available nodes.Tara KizerMicrosoft MVP for Windows Server System - SQL Serverhttp://weblogs.sqlteam.com/tarad/ |
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Cluster and High Availability