We need your help to make a decision.
First, we are application developers and maybe we are missing some important information to understand, so that's why we ask for your help.
We have deployed a "PI solution" all around the world and here is our current setup:
For each site:
2 VMware hosts with a SAN:
- PI Server 01 on the first, PI Server 02 on the second = PI Collective
- SQL Server 01 on the first, SQL Server 02 on the second = SQL cluster / mirror
- AF Server 01 on the first, AF Server 02 on the second = AF Collective
and other servers like services and terminal servers on both.
We do a lot of custom development currently with PI SDK.
Many of our custom applications need to write values in PI tags.
Everywhere we need to run our applications, we need to:
- Add a trust (admin) in PI for that client machine (needed by the buffering service);
- Setup the PI buffer sub service.
Doing this means that we lose the security set on pi tags?
All of this is a pain for us (developers) and we really want to revert to a non-collective PI. But first, we need good arguments to be able to convince higher instances.
Maybe we are wrong and we are going about it improperly?
We believe (developers) that all this "redundancy" is exaggerated since it is well taken care of by our VMware setup.
The fact that servers are virtual servers on 2 VMware hosts gives us enough fallback (VMware handling everything in case of maintenance/failure).
Also on another slightly related subject, with AF SDK 2.5’s PI namespace, there is no need any more for COM objects, which is GREAT!
But there is no support for the collective yet (forget about the SwitchMember hack since once a tag is buffered this does not work).
Our suggestion would be to remove all secondary servers from our solution and disable buffering, and then recover the ability to use the new AF SDK or the PI SDK to write/update/remove PI tags values from anywhere and with normal behavior.
Would you say this makes sense? Do you believe our understanding is right? Any advice that could help us make that decision would be appreciated?