The DS Placement and Scalability doc in KB29453 states this.
“The 32-bit console application does not scale beyond approximately 6 concurrent DS administrators without increasing the default refresh rate of the consoles. Its use is typically restricted to administrators who are local to the DS server, and remote administrators with high capacity WAN links (T3) back to the DS hosting site.”
One engineer reported that if the consoles are remote and going across a WAN connection and security is enabled, performance can be poor even with 3 or 4 consoles.
The deadlocks and performances all deal with how much is going on. There is no hard and fast rule about the number of connections. If for instance 10 out of 15 users in the console are imaging, it will be very slow and there could be performance issues for everyone. If they are just creating jobs, then there might be a few deadlocks, but it’s not likely.
The limitation is all relative to what you are doing with DS and your infrastructure. It depends on how it’s installed, if SQL is on box or off, how powerful SQL is, what kind of NIC the DS and SQL have, etc. The more requests that are hitting the same tables at the same time and the speed at which those requests are processed will determine if deadlocks occur. If deadlocks occur, generally only one of the requests will be processed. The others will be discarded. This could result in unexpected results.
I would also recommend that a frequent Defrag task be included on the SQL Server/DS maintenance plan in order to keep the drives optimized.