Thanks Andreas, I will try this and check. One of the issues I had, which really hasn’t helped is that some of the Dell server iDRACS are about 5 or 6 years old (iDRAC 8 with older firmware). I have had service checks running on occasions for over 13 minutes (these are snmp hosts) and then coming back with “item not found in monitoring data” for such things as temperatures of CPUs - the problem is that when I actually go to the iDRAC and check the values, they are actually not being shown to me, so check-mk is not wrong, it is only acting on the data it receives from the iDRAC - so there is a part of this issue that is most likely being caused by the old iDRACs themselves. I had to remove these old iDRAC hosts because they were causing bottlenecks in the checking - it seems to run much better on newer iDRAC9 servers.
I have quite a powerful server to run check-mk on, so I am confident it should be able to handle the number of hosts - the reason for this post was that I was looking for a way to be able to increase the number of processes that check-mk runs in order to do more in parallel when it comes to running these checks. Thanks again for the info.