September 10, 2010 at 7:13 am
We are purchasing a new 64 bit Intel Xeon 4 core sql server box 2008 with 256 GB RAM connected to high speed 15 K drives with fibre disc.
We are planning to consolidate our 3 sql server instances onto this one instance. Currently, the combined number of connections are roughly 400 and using around 50 GB RAM.
The new instance would therefore run around 15 applications that was previously divided into 3 instances. Are there any areas for concern regarding the performance of the new box. Is there anything else for me to consider/monitor/measure before we commit to doing this?
Do you think that having multiple instances on the same box would increase performance or would it be better to have instances on separate boxes.
September 11, 2010 at 5:19 am
Multiple instances are used not for increase overall performance, but for increase manageability.
One instance or three all share the same physical resources.
In my opinion one instance is better from performance point of view because SQL can optimize resource usage across all databases, while in 3 instances servers does not communicate with each other but compete for memory, CPU and disks.
You can use separate instances if you want to increase performance of one or few specific databases.
You may want to guarantee some memory and performance advantage to some particular databases. Then run this specific databases in separate instance and use minimum server memory for that instance. You can also make some CPUs available to one instance while not available to the rest.
Regards,
Slawek
September 11, 2010 at 10:06 pm
+1 to the prior poster.
I use multiple instances to use one physical machine and OSE (Operating System Environment) to serve up multiple copies of "the same" application database for different uses; one instance per developer, and the developers can restore from backups or make backups within the disk quota limits as they see fit (create a known starting point with whatever test data they need, and run tests from a well known starting point over and over).
For real production when you can combine databases properly (i.e. they all have different names), I'd use a single instance, and allow whichever needs it to use the resources required. All the usual caveats on virtualization apply; don't put two apps that need the full physical power during overlapping time periods on the same hardware, or they'll slow each other down. If one needs it Monday mornings, and another needs it every afternoon, you're fine. If they both need to meet SLA's at the same time... don't combine them casually.
September 12, 2010 at 12:19 am
I agree with the others on this.
One thing to note is that 15 applications / or 15 databases is not a burden for SQL server in many cases. There are other factors such as usage and how well the code is written and maintenance of the server that will affect overall performance for your apps.
Jason...AKA CirqueDeSQLeil
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