Question : How do I run rsync without it hogging resources?

I want to use rsync to back up uploaded files from a production server each day. The server is high-end (8 cores, 12GB ram) and runs a busy database. When i tried rsync it eventually killed the database, hogging all the cpu and memory. The source directory has approximately 500GB of files and once the first rsync operation has completed subsequent syncs should be faster.

How can I run rsync without it hogging resources?

Answer : How do I run rsync without it hogging resources?

You can throttle rsyc, which it appears you might need to do.  Use rsync --bwlimit=10000.

bwlimit sets bandwidth limits using KBytes per second...so For example, to limit I/O banwidth to 10000KB/s (9.7MB/s), enter 10000 like I did above.  Just pick a speed that works for you.