With the move to virtualisation and especially cloud its very easy to change the specification of your ArcGIS Server – increase cores, memory etc. While updating some tiles on a cache service the other day I noticed the number of caching service instances was set to 3 which was odd considering the AWS instance had 8 cores (originally it was 2 cores). A quick check in ArcGIS Manager and the caching tools were indeed set to maximum instances of 3 (i.e. 2 cores + 1). Changed this to 9 and the cache job was much faster. So remember to update the maximum instances for your caching tools service if you’ve changed the spec of your instance. Conversely, if you are decreasing your spec make sure to decrease the caching tools maximum instances or you’re going to have a bad time.