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How many mirrored databases can I have on a server?

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 How many mirrrored databases can I have on a server?

10 mirrored databases per server is the recommendation for a 32 bit computer WITH 4 processors or less. 64 bit computers have twice as many threads which means, in theory, that you can have twice as many mirrored databases. Also more processors = more threads = more mirrored databases. I interpolated the recommendations out from the base recommendation to other system profiles as follows: 

 

32-bit 64-bit
Number of CPUs Threads Mirrored Databases Threads Mirrored Databases
<= 4 processors 256 10 512 20
8 processors 288 11 576 22
16 processors 352 13 704 27
32 processors 480 18 960 37
 Others are correct to point out that this is a recommendation, not a hard limit. What your server can actually handle depends on the architecture as well as the amount of other traffic being handled by the server.

 

Comments
 

Jose Barreto's Blog said:

Here are some notes on “SQL Server 2008 Database Mirroring” I took while attending an advanced class

April 2, 2009 8:01 PM
 

Gé Brander said:

When you state 'processors' do you mean cores or processors? Do I need a 32 processor with quad cores ==> 128 cores or 8 processor with each 4 cores ==> 32 cores?

June 12, 2009 2:34 AM
 

Robert Davis said:

I use the term "processors" to mean logical processors. It is the number of processors as SQL sees them. So if you have 8 quad core processors, then SQL sees 32 processors. If you have 32 quad core processors, then SQL sees 128 processors.

June 14, 2009 6:00 PM
 

Gé Brander said:

Ok, clear. Maybe adjust your post to Cores. It makes more sense to people. Then you make a clear distinction between processors and cores.

June 15, 2009 4:30 AM
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