I suspect that reloading one a minute would affect your site performance but it would very much depend on:
- your configuration: what MPM are you using? prefork or worker? what is the number of children that you have specified? And in the case of worker, what is your max threads per child. This will affect how long the processes have to hang around due to the graceful nature of the shutdown.
- what people are doing on your site: are they downloading large files? this naturally leads to longer sessions and hence longer times for the processes to exit and be restarted
- what you are logging: this is somewhat related to the previous point but if you are logging bytes served then the log entry will only be made after the download session is completed.
- are you using Apache 2.2.12 or later: then you have the possibility of specifying a maximum time for "graceful" to work before the process is killed and restarted.
All of these will affect your response time to the reload. I think having a reload per minute is a bit excessive and will only degrade your site performance.
I'd suggest making a server HUP part of the process when a new config is rolled out as we do.
We've seen maximum traffic levels of 3.8 million hits per second and 7 million hits per second for over an hour during major news events and such an approach to config updates does not affect our servers.