I do have a SCCM 2012 SP1 CU4 environment. I do have a Primary with local SQL database, local MP and local SUP role. Beside that I do have a Secondary side in every world region.

The environment works fine, but except for the days when the patches are deployed to the clients. At that time the SCCM is very slow due to all the IIS activity to the server. (i think)

What I want to do now is to remove the MP and SUP role from my primary server and create dedicated servers for the MP and SUP roles. Also I want to use a SQL replica on the dedicated MP.

My question is how big will that SQL replica be on the dedicated servers with MP role ?

Will it be the same size as on my primary ? Are there known calculations for it how to size this on forehand ?

Can someone help me out or point me to the location were I can find the information ?

Thanks in advance.

Are you thinking the MP replica will be faster since the MP will access the replica and the replica will sync with the full DB?  I've seen replicas implemented in DMZs but I don't have experience with them for a purely performance standpoint.

SQL Replicas are generally small as they are only a replica of a small portion of the primary DB. For a real-world site containing nearly 100,000 clients, their SQL Replicas are about 15GB. No, there is no way to calculate this as it depends on many variables including client count and number or policies (among other things).

Note that SQL Replicas won't increase perf for your environment though unless you have a large population of clients not reporting to secondary sites (and instead reporting directly to the primary). Your clients within the scope of secondary sites are already using SQL replicas (MPs at secondary sites are effectively the same as SQL replicas).

So without knowing the breakdown of which client report where, there's no way to say whether this will help or not.

Also, do you have SUPs at all of these locations co-located with the secondary sites or do you have a single SUP on the primary site?

SQL Replicas are generally small as they are only a replica of a small portion of the primary DB. For a real-world site containing nearly 100,000 clients, their SQL Replicas are about 15GB. No, there is no way to calculate this as it depends on many variables including client count and number or policies (among other things).

Note that SQL Replicas won't increase perf for your environment though unless you have a large population of clients not reporting to secondary sites (and instead reporting directly to the primary). Your clients within the scope of secondary sites are already using SQL replicas (MPs at secondary sites are effectively the same as SQL replicas).

So without knowing the breakdown of which client report where, there's no way to say whether this will help or not.

Also, do you have SUPs at all of these locations co-located with the secondary sites or do you have a single SUP on the primary

Adding an additional MP for the primary will have no effect on clients using secondary sites -- they don't truly care about or use the MPs in the primary for day-to-day activity like deployments so adding an additional one is meaningless.

With 20,000 clients hitting your single SUP on the primary site, yes, I would say this is absolutely a bottleneck which you can address by adding additional SUPs to the primary or by adding SUPs to the secondary sites. I would start with the first option and see if that helps.